REESE       [BRARY 


UNIVERSITY  OF  CALIFORNIA. 

,  i8i)J. 
.   Class  No. 


&£  -  W'^^^^^^^: 


•mm 


A  COMPLETE  TREATISE 


ON    THE 


ELECTRO-DEPOSITION  OF  METRLS. 


COMPRISING 

ELECTRO-PLATING  AND  GALYANOPLASTIC  OPERATIONS,  THE  DEPOSITION 

OF  METALS  BY  THE  CONTACT  AND  IMMERSION  PROCESSES, 

THE  COLORING  OF  METALS,  THE  METHODS  OF 

GRINDING  AND  POLISHING, 

AS    WELL    AS 

DESCRIPTIONS  OF  THE  ELECTRIC   ELEMENTS,  DYNAMO-ELECTRIC 

MACHINES,  THERMO-PILES,  AND  OP  THE  MATERIALS  AND 

PROCESSES  USED  IN  EVERY  DEPARTMENT  OF  THE  ART. 


TRANSLATED  FROM  THE  GERMAN  OF 

DR.  GEORGE   LANGBEIN, 

PROPRIETOR  OF  A  MANUFACTORY  FOR  CHEMICAL  PRODUCTS,   MACHINES,   APPARATUS, 

AND  UTENSILS  FOR  ELECTROPLATERS  AND  OF  AN  ELECTRO-PLATING 

ESTABLISHMENT,   IN   LEIPZIG. 


WITH  ADDITIONS  BY 

WILLIAM  T.  BRANNT, 

EDITOR  OF  "THE  TECHNO-CHEMICAI^  RECEIPT  BOOK." 

THIRD  EDITION,  THOROUGHLY  REVISED  AND  MUCH  ENLARGED. 
ILLUSTRATED  BY  ONE   HUNDRED  AND   FIFTY   ENGRAVINGS. 


PHILADELPHIA  : 
HENRY   CAREY   BAIRD   &   CO., 

INDUSTKIAL  PUBLISHEKS,  BOOKSELLEKS,  AND  IMPOETEKS. 
810  WALNUT  STREET. 

1898. 


COPYRIGHT  BY 
HENEY  CAEEY  BAIKD  &  CO., 

1898. 


7V  7*? 


PRINTED  AT  THE 

WICKERSHAM  PRINTING  HOUSE, 

53  and  55  North  Queen  Street, 

LANCASTER,  PA.,  U.  S.  A. 


PREFACE  TO  THE  THIRD  BMERICflN  EDITION. 


THE  rapid  sale  of  the  second  American  edition  of  Dr.  George 
Langbein's  work,  "  Handbuch  der  Galvanischen  Metall-Nieder- 
schlaege"  and  the  constant  demand  for  it,  are  the  best  proofs 
of  the  value  and  usefulness  of  the  book. 

In  the  third  edition,  which  is  now  presented  to  the  public,  no 
changes  have  been  made  in  the  arrangement  of  the  text,  and 
it  has  been  endeavored  to  include  all  practical  methods  of  plat- 
ing metals  which  have  become  known  since  the  publication  of 
the  first  and  second  editions,  as  well  as  the  most  recent  ma- 
chinery and  apparatus,  so  as  to  make  the  work  still  more  ac- 
ceptable and  useful  to  the  reader. 

The  editor  is  under  obligations  for  information  and  electro- 
types to  the  Hanson  &  Van  Winkle  Co.,  of  Newark,  N.  J.,  the 
well-known  firm  dealing  in  electro-platers'  supplies ;  to  the 
Electro- Chemical  Storage  Battery  Co.,  of  New  York  City,  and 
to  Mr.  Bossard,  inventor  of  the  Bossard  Mechano-Electro- 
plating.  Tanks. 

The  publishers  have  spared  no  expense  in  the  proper  illus- 
tration and  the  mechanical  production  of  the  work,  and,  like  the 
previous  editions,  it  has  been  provided  with  a  copious  table  of 
contents  and  a  very  full  index,  so  as  to  render  reference  to  any 
subject  prompt  and  easy. 

W.  T.  B. 

PHILADELPHIA,  February  I,  1898. 

(Hi) 


PREFACE  TO  THE  FIRST  flMERICAN  EDITION. 


THE  art  of  the  electro-deposition  of  metals  has  during  recent 
years  attained  such  a  high  degree  of  development,  that  it  was 
felt  that  a  comprehensive  and  complete  treatise  was  needed  to 
represent  the  present  advanced  state  of  this  important  industry. 
In  furtherance  of  this  object,  a  translation  of  Dr.  George  Lang- 
bein's  work,  Vollsiaendiges  Handbuch  der  Galvanise  hen  Metall- 
Niederschlaege,  is  presented  to  the  English-reading  public  with 
the  full  confidence  that  it  will  not  only  fill  a  useful  place  in 
technical  literature,  but  will  also  prove  a  ready  book  of  reference 
and  a  practical  guide  for  the  workshop.  In  fact,  it  is  especially 
intended  for  the  practical  workman,  wherein  he  can  find  advice 
and  information  regarding  the  treatment  of  the  objects  while  in 
the  bath,  as  well  as  before  and  after  electro-plating.  The  au- 
thor, Dr.  George  Langbein,  is  himself  a  master  of  the  art,  being 
the  proprietor  of  an  extensive  electro-plating  establishment 
combined  with  a  manufactory  of  chemical  products,  machinery 
and  apparatus  used  in  the  industry. 

The  results  yielded  by  the  modern  dynamo-electric  machines, 
to  which  the  great  advance  in  the  electro-plating  art  is  largely 
due,  are  in  every  respect  satisfactory,  and  the  more  so  since  the 
need  of  accurate,  and  at  the  same  time  handy,  measuring  in- 
struments has  also  been  supplied.  With  the  assistance  of  such 
measuring  instruments,  the  establishment  of  fixed  rules  regard- 
ing the  current-conditions  for  a  galvanic  bath  has  become  pos- 
sible, so  that  good  results  are  guaranteed  from  the  start.  While 
formerly  the  electro-plater  had  to  determine  the  proper  current- 
strength  for  the  depositions  in  an  empirical  manner,  by  time- 
consuming  experiments,  to-day,  by  duly  observing  the  deter- 

(v) 


VI  PREFACE   TO   THE   FIRST   AMERICAN   EDITION. 

mined  conditions  and  provided  with  well-working  measuring 
instruments,  he  can  at  once  produce  beautiful  and  suitable  de- 
posits of  the  various  metals. 

The  data  referring  to  these  current-conditions,  according  to 
measurements  by  Dr.  Langbein,  are  given  as  completely  as  pos- 
sible, while  for  the  various  baths,  only  formulae  yielding  entirely 
reliable  results  have  been  selected.  To  most  of  the  baths  a 
brief  review  of  their  mode  of  action  and  of  their  advantages  for 
certain  uses  is  added,  thus  enabling  the  operator  to  select  the 
bath  most  suitable  for  his  special  purpose.  To  the  few  formulae 
which  have  not  been  tested,  a  note  to  that  effect  is  in  each  case 
appended,  and  they  are  only  given  with  due  reserve. 

To  render  the  work  as  useful  as  possible,  the  most  suitable 
formulae  for  plating  by  contact  and  immersion,  as  well  as  the 
best  methods  for  coloring  the  metals,  and  the  characteristic 
properties  of  the  chemicals  used  in  the  industry,  are  given. 
However,  the  preparation  of  the  chemicals  has  been  omitted, 
since  they  can  be  procured  at  much  less  expense  from  chemi- 
cal works  than  it  would  be  possible  for  the  electro-plater  to 
make  them  in  small  quantities,  even  if  he  possessed  the  neces- 
sary apparatus  and  the  required  knowledge  of  chemistry  and 
skill  in  experimenting. 

If  is  hoped  that  the  additions  made  here  and  there  by  the 
translator,  as  well  as  the  chapter  on  "  Apparatus  and  Instru- 
ments," and  that  of  "  Useful  Tables,"  added  by  him,  may  con- 
tribute to  the  usefulness  of  the  treatise. 

Finally,  it  remains  only  to  be  stated  that  the  publishers  have 
spared  no  expense  in  the  proper  illustration  and  the  mechani- 
cal production  of  the  book;  and,  as  is  their  universal  practice, 
have  caused  it  to  be  provided  with  a  copious  table  of  contents, 
and  a  very  full  index,  which  will  add  additional  value  by 
rendering  any  subject  in  it  easy  and  prompt  of  reference. 

W.  T.  B. 

PHILADELPHIA,  July  i,  1891. 


CONTENTS 


HISTORICAL  PART. 

CHAPTER  I. 
HISTORICAL  REVIEW  OF  ELECTRO-METALLURGY. 

PAGK 

The  method  of  coating  metals  by  simple  immersion,  known  to  Zozimus 
and  Paracelsus ;  Luigi  Galvani's  discovery,  in  1789,  of  the  electric 
contact-current ;  Alexander  Volta's  discovery,  in  1799,  °f  the  true 
causes  of  the  electric-contact  current;  Galvani's  experiments  .  .  I 

Erroneous  inference  drawn  by  Galvani  from  his  experiments  ;  General 
ignorance  in  regard  to  the  electric  current;  Discovery  which  led  to  the 
construction  of  the  pile  of  Volta,  or  the  voltaic  pile  ;  Cruikshank's 
trough  battery .  .  ...  .  .  .  .  .  .  .  .2 

Decomposition  of  water  by  electrolysis  by  Nicholson  and  Carlisle,  1800 ; 
Wollaston's  observations,  1801  ;  Cruikshank's  investigations,  1803  ; 
Brugnatelli's  experiments  in  electro-gilding,  1805 ;  Sir  Humphrey 
Davy's  discovery  of  the  metals  potassium  and  sodium,  1807 ;  Prof. 
Oersted's  discovery  of  the  deflection  of  the  magnetic  needle,  1820  .  3 

Construction  of  the  galvanoscope  or  galvanometer;  Ohm's  discovery,  in 
1827,  of  the  law  named  after  him  ;  Faraday's  discover}7,  in  1831,  of 
electric  induction  ;  First  electro-magnetic  induction  machine  con- 
structed by  Pixii;  Faraday's  electrolytic  law  laid  down  and  proved  in 
1833 !  Production  of  iridescent  colors,  in  1826,  by  Nobili ;  Production 
of  the  amalgams  of  potassium  and  sodium,  in  1853,  by  Bird  ;  Discov- 
ery of  the  actual  galvano-plastic  process,  in  1838,  by  Prof.  Jacobi  .  4 

Claims  of  priority  of  invention  by  Mr.  T.  Spencer  and  Mr.  C.  J.  Jordan  ; 
I/abors*  of  the  Elkingtons  and  of  De  Ruolz ;  Murray's  discovery  in 
1840,  of  black-leading;  Introduction,  in  1843,  °f  gutta-percha  by  Dr. 
Montgomery;  First  employment,  in  1840,  of  alkaline  cyanides  by 
Wright  .  5 

Patent  for  the  deposition  of  nickel,    1840  ;    Origination   of  the  term 


Vlll  CONTENTS. 


"electro-metallurgy,"  by  Mr.  Alfred  Smee,  1841  ;  Prof.  Boettger's  dis- 
covery, in  1842,  of  the  deposition  of  nickel  from  its  double  salt ;  First 
deposition  of  metallic  alloys  by  De  Ruolz  ;  First  use  of  thermo- 
electricity, in  1843,  by  Moses  Poole ;  Advances  in  the  art  of  electro- 
deposition  .......  ..... 

The  first  magnetic  machine  that  deposited  silver  on  a  practical  scale, 
constructed,  in  1844,  by  Woolrych  ;  Attempts,  since  1854.  by  Christofle 
&  Co.  to  replace  their  batteries  by  magneto-electrical  machines ;  The 
Alliance  machine  ........... 

Objections  to  Wilde's  machine  ;  Dr.  Antonio  Pacinotti's  invention,  in 
1869,  of  the  ring  named  after  him  ;  Siemens'  dynamo  machine,  1866  ; 
Wheatstone's  dynamo  machine,  1867  ;  Introduction,  in  1871,  of  Zen- 
obe  Gramme's  machine  ;  The  Hefner-Alteneck  machine,  1872  ;  Sie- 
mens &  Halske's  machine,  1884;  S.  Schuckert's  machine,  1884;  Vari- 
ous dynamo-electrical  machines  .  .  .  .  .  .  . 

Investigators  and  practitioners  who  have  contributed  to  the  improve- 
ment of  the  electro-chemical  processes  and  the  perfection  of  galvano- 
plasty  .  .  .  .  


II. 

THEORETICAL  PART. 

CHAPTER  II. 
MAGNETISM  AND  ELECTRICITY. 

i.  MAGNETISM. 

Loadstone  or  magnetic  iron  ore ;  Natural  and  artificial  magnets  ;  Defi- 
nitions of  the  magnetic  poles  and  of  the  neutral  line  or  neutral  zone, 
and  their  positions  .  .  .  .  .  .  .  .  .  .  .10 

Magnetic  meridian  ;  North  and  south  poles  ;  Phenomena  of  attraction 
and  repulsion;  Ampere's  theory  .  .  .  .  .  .  .  .11 

The  solenoid  ;  Rejection  of  Ampere's  theory  by  many  scientific  men  ; 
Definition  of  the  magnetic  field 12 

II.   ELECTRICITY. 

Definition  of  idio-electrics  and  non-electrics;  Gray's  discovery,  1727; 
Good  and  bad  conductors;  The  electroscope;  Existence  of  two  kinds 
of  electricity  ;  Vitreous,  or  positive,  and  resinous,  or  negative,  elec- 
tricity    13 


CONTENTS.  ix 

PAGE 

Double  fluid  hypothesis  of  electricity  ;  Single  fluid  hypothesis  of  elec- 
tricity .  .  .  .  ...  .  .  .  .  .  .14 

Investigations  of  Prof.  Herz,  1889  ;  Colomb's  law  ;  Series  of  electro- 
motive force  or  tension  ;  Production  of  electricity  by  the  contact  of 
metals  and  fluids  ...........  15 

The  galvanic  current  or  hydro-electric  current ;  Galvanic  element  or 
galvanic  chain;  Electrical  potential;  Electro-motive  force;  Resistance.  16 

Conductivity  of  metals  according  to  Lazere  Weiler;  Quantity  of  current 
— Ohm's  law 17 

Essential  or  internal  resistance;  Non-essential  or  external  resistance      .     18 

Union  or  coupling  of  the  elements  for  electro-motive  force  or  tension  ; 
Coupling  for  quantity  of  current ;  Mixed  coupling  .  .  .  .20 

Proposition  deduced  from  Ohm's  law;  Effects  of  the  electric  current      .     21 

Electro-magnetism. 

Rule  for  determining  the  direction  which  the  magnetic  needle  will  as- 
sume when  placed  in  any  particular  position  to  the  conducting  wire  .  21 

Galvanoscopes,  galvanometers,  or  multipliers;  The  astatic  galvanome- 
ter ;  The  tangent  galvanometer ;  The  sine  galvanometer  .  .  .22 

Electro-magnets  ;  The  solenoid  ;  Law  of  the  action  of  two  electrified 
wires  on  each  other .  .  .  ....  .  .  .  .23 

Induction. 

What  is  understood  by  induction         .       '.         *         .         .         .         .  .23 

Primary  or  inductive  current ;  Secondary  or  induced  current .        .  .24 

Alternating  currents  ;  Extra  currents .     25 

Chemical  Actions  of  the  Electric  Current — Electrolysis. 

Reduction  of  the  constituents  of  a  fluid  by  the  electric  current ;  Pure 
water  a  bad  conductor  .  .  .  .  .  .  .  .  .  .25 

Faraday's  discovery  of  the  chemical  actions  of  the  electric  current ; 
Electrolysis  ;  Electrolyte  ;  Electrodes  ;  Anode  ;  Cathode  ;  Ions  ;  Ani- 
ons  ;  Cations  ;  Atoms  ;  Clausius'  theory  of  the  molecules  .  .  .26 

Counter  or  polarizing  current;  Faraday's  electrolytic  laws  ;  Experi- 
ments with  the  voltmeter .  .27 

Local  action  ;  Electro-chemical  equivalents  ;  Joule's  law         .        .        .29 

Consumption  of  power  in  electrolysis  ;  Electric  units  adopted  by  the 
International  Congress  of  1881 ;  Fundamental  or  C.  G.  S.  (centimetre- 
gramme-second)  system  ;  Force  or  power — dyne  ;  Work — erg  ;  Quan- 
tity ;  Potential  or  electro-motive  force  ;  Resistance  .  .  .  .30 

The  ohm  ;  The  ampere ;  The  volt ;  The  farad  ;  The  coulomb ;  The  watt; 
Definition  of  the  English  and  of  the  French  horse-power  .  .31 


CONTENTS. 


SOURCES  OF  CURRENT. 

CHAPTER  III. 

GALVANIC  ELEMENTS — THERMO-PILES—MAGNETO-  AND  DYNAMO- 
ELECTRIC  MACHINES. 

A.  GALVANIC  ELEMENTS. 

The  voltaic  pile  ;  Trough  battery 32 

Reduction  of  local  action  by  amalgamating  the  zinc  ;  Various  ways  of 

amalgamation  ............     33 

Bruant's  recommendation  ;  Definition  and  cause  of  polarization  ;  Smee's 

element     .         .',„-...         .         .         .         .         .         .        .         .34 

Constant  elements  ;  Daniel's  element        .......     35 

Meidiuger  element       . .36 

Grove  element ;  Bunsen  elements 37 

Improved  Bunsen  cell  ..........     39 

Electropoion  and  its  composition  ;  Location  of  elements  ;  Dupre"'s  sub- 
stitute for  sulphuric  and  nitric  acids  for  filling  elements       .        .         .40 
A  soluble  chromium  combination  which  depolarizes  with  rapidity  ;  In 

spection  and  cleansing  of  the  binding  screws        .         .         .         .         .41 

Manipulation  of  Bunsen  elements       ........     42 

Advisability  of  having  a  duplicate  set  of  porous  clay  cells  ;  Renewal  of 

the  acids;  Foote's  pinnacle  gravity  battery 43 

Oppermann's  element          ..........     44 

The  I/eclanche  element;  Lallande  and  Chaperon  element        .         .         .48 
The  cupron  element    .         .         .         .         .         .         .        .         .         .         .50 

Various  elements  ;  Duns'  potash  element .......     51 

Element  patented  by  Knaffe  and  Kiefer,  of  Vienna 52 

Plunge  or  bichromate  batteries  ;  The  Bunsen  plunge  battery  ;   Fein's 

bichromate  battery  ...........     53 

Keiser  &  Schmidt's  bichromate  battery 54 

Bichromate  element  for  gilding  or  silvering  small  articles        .         .         .55 
Stcehrer's  battery  ;  Plunge  battery  manufactured  by  Dr.  G    Langbein 

&  Co .56 

B.  THERMO-ELECTRIC  PILES. 

Prof.  Seebeck's  discovery,  in  1822,  of  a  new  source  of  electricity     .         .  57 
Definition  of  a  thermo-electric  couple  and  of  thermo-electricity;  Noe's 

thermo-electric  pile  ;  Clatnond's  thermo-electric  pile    ....  58 

Hauck's  thermo-electric  pile      .........  59 

Gulcher's  thermo-electric  pile    .........  60 

Superiority  of  dynamo-electric  machines  over  thermo-electric  piles        .  62 


CONTENTS.  xi 


C.  MAGNETO-  AND  DYNAMO -ELECTRIC  MACHINES. 

Faraday's  discovery,  in  1831       .........     62 

Magnetic  field,  or  the  region  of  the  lines  of  force  ;  What  a  magneto- 
electric  or  dynamo-electric  machine  actually  is  .         .         .         .63 

Prof.  S.  P.  Thompson's  definition  of  a  dynamo-electric  machine     *        .     64 
Pixii's  electrical  machine,  1832  ;  Saxton  and  Clarke's  improvements ; 
Dr.  W.  Siemens'  improvement,  1857;  Pacinotti's  ring  conductor,  1860; 
Dr.  W.  Siemens'  and  Sir.  C.  Wheatstone's  discovery     .         .         .         .65 

Classes  of  electric  generators  ;  Continuous  current  and  alternating  cur- 
rent machines  ;  The  Gramme  machine  .......     66 

The  Gramme  armature  ;  Modern  Gramme  dynamo  for  galvanoplastic 
purposes    .............     67 

Disadvantage  of  the  Gramme  machine      .......     68 

S.  Schuckert's  flat  ring  machine 69 

Fein's  dynamo  machine  ;  The  Brush  dynamo 70 

The  ring  of  the  Brush  dynamo   .........     71 

Siemens'  and  Halske's  dynamo-electric  machines    .         .         .         .         .72 

Krcettlinger  dynamo    ...........     74 

Lahmeyer  dynamo 75 

Resume  of  the  evolution  of  the  dynamo  for  plating  purposes  in  the 

United  States  ;  The  Weston  dynamo 77 

"Little  Wonder"  dynamo -      .         .         .         .         .78 

The  "H.  &  V.  W."  dynamo       .        .        .        •.        .         .         .        .         .     79 

The  new  "H.  &  V.  W."  dynamo       .        .        ,        .        .         .        .         .81 

Advantages  claimed  for  the  new  "  H.  &  V.  W."   dynamo  ;    Various 

dynamo  machines    .         .        .        . 83 

Value  of  the  dynamo,  and  its  effect  upon  the  electro-plating  industry  ; 
Data  for  the  most  suitable  machine        .         .        .        *        .         .  84 


IV. 
PRACTICAL    PART. 

CHAPTER  IV. 
ARRANGEMENT  OF  ELECTRO-PLATING  ESTABLISHMENTS  IN  GENERAL. 

Necessity  of  sufficient  light  and  thorough  ventilation  .  .  .  .85 
Location  of  Bunsen  elements;  Provision  for  heating  .  .  .  .86 
Importance  of  a  good  supply  of  water;  Best  materials  for  floors;  Size 

of  the  operating  room .87 

Grinding  and  polishing  rooms    .         .         .         .         ...        ,         .     88 

Prevention  of  dust  in  the  polishing  room;  Location  of  the  transmission 

carrying  the  belt-pulleys       .        .        .         .        .         •.,-..•,,        .        .     89 


Xll  CONTENTS. 


ELECTRO-PLATING   ARRANGEMENTS   IN    PARTICULAR. 

Parts  constituting  the  actual  electro-plating  plant ;  Arrangement  with 
elements   ........*..-..     89 

Choice  of  coupling  the  elements;  Proportion  of  the  effective  zinc  surface 
of  the  elements  to  that  of  the  anodes  and  articles  .         .         .         .90 

Requisites  as  regards  the  result  of  the  process  of  deposition    .         .         .91 
Coupling  of  elements  for  solid  and  thin  deposits       .         .         .         .         .92 

Auxiliary  apparatus;  The  rheostat,  current-regulator,  resistance  board 

or  switch  board .93 

Conditions  upon  which  the  action  of  the  resistance  board  is  based  .         .     94 
Horizontal  and  vertical  galvanometers       .         .         .         .         .         .         .95 

Location  of  the  resistance  board  and  galvanometer  ;  Improved  switch- 
board or  rheostat  .  .  •  .  .  ...  .  .  .  .96 

Indications  made  by  the  galvanometer 97 

The  Weston  voltmeter .  100 

The  Weston  ammeter;  Rules  to  be  observed  in  conducting  the  current  .  102 
Positive  or  anode  wire;  Negative  or  object  wire;  Vats  or  tanks        .         .  103 

Wooden  vats;  Wooden  vats  lined  with  sheet  lead 104 

Enameled  iron  vats;  Agate  vessel  for  gold  and  other  solutions         .         .105 
Conducting  rods;  Anodes  and  their  arrangement      .....  106 

Binding  posts  and  screws;  Mode  of  suspending  the  anodes       .         .         .  107 
Mode  of  suspending  the  objects;  Slinging  wires;  Protection  of  the  con- 
ducting rods;  Cleansing  and  rinsing  apparatuses  .....  108 

Dipping   or  pickling ;  Sawdust ;    Arrangements   with   dynamo-electric 
machines  ;     Rules     for     setting-up     and     running    dynamo-electric 
machines  ............  109 

Insulation  of  the  object  and  anode  wires  ;  Special  wire  carriers  ;  Ar- 
rangement with  one  machine  which  has  to  feed  several  baths;  Loca- 
tion of  the  dynamo  resistance-board  .  .....  110 

The  amperemeter  or  ammeter;  The  voltmeter 113 

Coupling  of  the  main  object  wire  with  the  main  anode  wire,  with  the  re- 
sistance board,  the  voltmeter,  the  shunt,  and  the  two  baths          .         .  114 
Ground  plan  of  an  electro-plating  establishment       .         .         .         .         .116 

Table  for  freeing  the  articles  from  grease  .         .         .         .         .         .119 

Plating  room  arranged  by  the  Hanson  &  Van  Winkle  Co.,  of  Newark, 
N.  J. ;  Mode  of  calculating  the  thickness  of  conducting  wire  for 
dynamos  .............  120 

CHAPTER  V. 
TREATMENT  OF  METALLIC  ARTICLES. 

A.  MECHANICAL  TREATMENT. 
Treatment  before  electro-plating  ;  Scratch  brushing  ;  Formation  of  the 

deposit  in  correspondence  with  the  surface  of  the  basis-metal       .         .   122 
Modes  of  scratch-brushing  ;  Various  forms  of  scratch  brushes          .         .  123 


\ 

CONTENTS.  xiii 


Treatment  of  scratch-brushes  ;  Circular  scratch-brushes  ....  124 

Circular  scratch-brush  for  cleansing  purposes,  and  its  construction          .  125 
Brushes         .         .      •  -.      '  .         .         .         .         .         ...         .         .  126 

Cleansing  by  the  sand  blast         .         .         ...»         .         .         .         .  127 

Tumbling  drum  or  box         ..*'..         .         .         .         .         .         .         .  128 

Improved  exhaust  tumbling  barrel     .         ....         .         .         .         .  129 

Mode  of  polishing  articles  in  the  tumbling  drum      .....  130 

Grinding;  Grinding  disks  and  their  construction;  Roughing  wheel, 

medium  wheel  and  fine  wheel      4   .         .         .         .         .         .         .         .   132 

Treatment  of  the  grinding  disks  ;  Vienna  lime  ;  Grinding  lathes    .         .   133 
Execution  of  grinding      '  .         .         .         .  .         .         ,         .         .  134 

Fibres  and  fibre-brushes ;  Grinding  iron  and  steel  articles        .         .         .  135 
Grinding  brass  and  copper  castings  ;  Treatment  of  sheets  of  brass,  Ger- 
man silver,  and  copper  ;  Treatment  of  zinc  castings  and  sheet  zinc      .  136 
Polishing;  Foot  lathe  for  polishing  ;   "  Compress  "  polishing  wheels      .  137 
Foot  lathe  for  light  grinding,  polishing  and  buffing.         .         .         .         .  138 

American  double-polishing  lathe;  Lathe  manufactured  by  the  Hanson  & 

Van  Winkle  Co.,  of  Newark,  N.  J.  ....         .         .         .         .139 

Glue  pot        ....         .         .        ...         .         .        .  -.      .  141 

Belt  strapping  attachment  or  endless  belt  machine  .         »         ••.,••         •  142 
Flexible  shaft  for  grinding,  polishing  and  buffing     .         .         .         .         .  143 

Polishing  materials  ;  Rouge  composition  ;  Burnishing     .         .         .         .  144 

Mechanical  treatment  during  and  after  the  electro-plating  process ; 

Scratch-brushing  the  deposits          ,         .         .         .         .....   145 

Effect  of  scratch-brushing  ;  Scratch-brushes  used  for  different  metals ; 

Decoctions  used  in  scratch-brushing  ;  Scratch-brushing  by  hand         .   146 
Lathe  brush.         ............  147 

Treatment  of  the  finished  electro  plated  objects;  Sawdust  for  drying  the 

objects  ;  Method  of  freeing  nickeled  objects  from  moisture  .  .  .  148 
Polishing  deposits  of  nickel,  copper,  brass,  tin,  gold  and  silver,  and 

platinum;  Operation  of  burnishing  and  forms  of  burnishers        .         .  149 

B.    CHEMICAI,  TREATMENT. 

Pickling  ;  Mixture  for  pickling  cast  iron  and  wrought  iron  objects         .   150 
Excellent  pickle  for  iron  ;  To  cleanse  badly-rusted  iron  objects  ;  Dura- 
tion of  pickling  ;  Pickling  zinc  objects  ;  Cleansing  and  brightening 
copper,  brass,  bronze,  tombac,  and  German  silver         .         .     -    .         .  151 
Preliminary  pickle  ;  Bright  dipping  bath  ;  Use  of  potassium  cyanide  for 

pickling;  Manipulation  of  pickled  objects 152 

Preparation  of  a  good  dead  dip  ;  Main  points  in  pickling         .     ...        .  153 

Absorbing  plant  for  escaping  acid  vapors  .         .         .         .         .   .      .  154 

Regaining  of  acid  and  metal  from  exhausted  dipping  baths  •  -.         .  155 

Mixture  for  the  production  of  a  grained  surface  ;  Removal  of  grease       .  156 
Preparation  of  lime  mixture  ;  Cleansing  with  benzine      ....  157 

Tying  the  objects  to  metallic  wires;  Removal  of  oxide  from  the  metallic 
objects;  Steel  spring  carboy  rocker          .         .         .         .         .         .         .158 


xiv  CONTENTS. 

PAGE 

CHAPTER  VI. 
PROCESSES  OF  ELECTRO-DEPOSITION. 

Importance  of  the  constitution  of  the  water  used  as  a  solvent;  Spring 
and  well  water;  Rain  water  .  .  ......  159 

Importance  of  the  purity  of  the  chemicals  used         .         .        .  .160 

Concentration  of  the  baths;  Non-reliability  of  measurement  by  hydro- 
meter degrees 161 

Effects  of  baths  too  poor  in  metal  and  too  concentrated;  Stirring  up  the 
baths 162 

Effect  of  heavier  and  more  saturated  fluid  on  the  anodes;  Constant 
agitation  of  the  baths  by  mechanical  means  ......  163 

Temperature  of  the  baths;  Boiling  of  the  baths;  Kettles  and  boiling 
pans  .............  164 

Working  the  bath  with  the  electric  current  in  place  of  boiling;  Dissolu- 
tion of  nickel  salts  dissolving  with  difficulty  .  . .  .  .  .  .  165 

Filtration  of  the  boiled  solutions;  Means  of  securing  lasting  qualities  to 
the  baths;  Choice  of  anodes  .  .  ; 166 

Alloying  of  the  deposit  with  the  basis-metal;  Gore's  experiments;  Con- 
ditions for  the  good  performance  of  an  electrolytic  bath  .  .  .167 

Reduction  of  metals  without  a  battery  (electro-deposition  by  contact); 
Reduction  of  metal  by  dipping  one  metal  into  one  fluid  .  .  .168 

CHAPTER   VII. 

DEPOSITION  OF  NICKEL  AND  COBALT. 
i.  NICKELING. 

Growth  and  popularity  of  nickel-plating;  Properties  of  nickel        .         .169 
Nickel  baths;  General  rules  for  preparing  nickel  baths    .         .         .         .170 
The  active  constituent  in  many  prepared  nickeling  salts;  Use  of  the 
chlorine  combinations;  Additions  to  the  nickeling  bath  recommended 
by  various  experts;  Effects  of  the  presence  of  small  quantities  of  a 
free  acid;  Boric  acid  as  an  addition  to  nickeling  and  all  other  baths, 

and  its  effects 171 

Determination  of  the  acidity,  alkalinity,  and  neutrality  of  nickel  baths  .  172 
Formulae,  preparation,  characteristics  and  treatment  of  nickel  baths  .  173 
Burning  or  over-nickeling  .  .  .  T  .  .  .  .  •  .  .  174 
Nickel  baths  containing  boric  acid;  Weston's  bath  .....  175 

Kaselowsky's  formula 176 

Proportion  of  cast  to  rolled  anodes     .        . 177 

Bath  for  rapid  nickeling  of  polished,  slightly  coppered  zinc  articles; 
Nickel  bath  for  iron,  brass  and  copper,  and  sheet  zinc  and  zinc 

castings     .... 178 

Compositions  of  a  few  nickel  baths  which  have  been  highly  recom- 


CONTENTS.  XV 

PAGE 

meiided;   An  English  formula;  Addition  of  bisulphide  of  carbon  to 
nickel  baths;  Bath  for  nickeling  small  articles      .....  179 

Nickel  baths  without  nickel  salts;  Nickel  anodes 180 

Objections  to  insoluble  anodes   .........  181 

Use  of  rolled  and  cast  anodes  together  in  one  bath;  Size  of  anode- 
surface  183 

Cause  of  the  reddish  tinge  of  the  anodes;  Manner  of  suspending  the 
anodes;  The  process  of  electro-nickeling        ......  184 

Coppering  or  brassing  articles  previous  to  nickeling         ....  185 

Suspension  of  the  objects  in   the  bath;  Suitable   current-strength   for 

nickeling 186 

Burning  or  over-nickeling  ;  Criteria  for  judging  whether  nickeling  pro- 
gresses with  a  correct  current-strength  .......  187 

Most  suitable  current-density  for  nickeling       ......  188 

Solid  nickeling  ;  Test  for  sufficient!}'  heavy  nickeling      ....  189 

Arrangement  of  the  anodes  ;  Nickeling  of  flat  objects  ;  Round  or  half- 
round  surfaces  ;  Smooth  articles ;  Objects  with  depressions  and  hol- 
lows, and  lamp  feet  of  cast  zinc       ........  190 

Additional  rules  for  nickeling  and  other  electro-plating  processes;  Mode 
of  suspending  objects  with  depressions  and  hollows  in  the  bath;  Polar- 
izing phenomena      ..       ......        .         .         .         .         .         .  191 

Nickeling  en  masse  of  small  and  cheap  objects          .....  193 

Warren's  solutions  of  nickel  and  of  cobalt  to  be  decomposed  in  a  sim- 
ple cell  apparatus;  Stripping  nickeled  articles       ......  194 

Stripping  acid      .         .         .        .         .         .         .         .         .  .         .  195 

Stripping  by  means  of  the  battery  or  the  dynamo;  Remedy  against  the 
yellowish  tone  of  nickeling ;  Resume  of  the  principal  phenomena 
which  may  occur  in  nickeling  .  .  .  .  .  .  .  .  196 

Refreshing  nickel  baths .         .        .        .198 

Polishing  nickel  deposits  ;  Treatment  of  nickeled  articles  which  are  to 
be  left  dead;  Nickeling  sheet  zinc ;  Mystery  with  which  the  nickeling 

of  sheet  zinc  has  been  surrounded 199 

Conditions  required  for,  and  the  execution  of  nickeling  sheet  zinc  ;  Pre- 
liminary grinding  or  polishing  ;  Construction  of  cloth  bobs          .         .  200 
Mode  of  polishing  or  grinding  the  sheets  .         ....'.         .  201 
Self-acting  sheet  polishing  machines ;  F.  Rauber's  sheet  grinding  and 

polishing  machine    .         .         .        . 202 

Freeing  the  sheets  from  grease  .         ......         .        .  204 

Nickeling  the  sheets  ;  Advantage  of  previous  coppering  or  brassing        .  205 
Prevention    of  the  peeling  off  of  the  nickel  deposit ;  Coppering   the 

sheets        .         .         .         . 206 

Dimensions  of  vats  for  nickeling  the  sheets  ;  Proportion  of  anode-surface 
to  zinc-surface  .         .        .         ...      *     .    ,    ti .  .        <.         .    ,     .         .  207 

Cause  of  black  streaks  and  stains ;  Augmentation  of  the  metallic  content 
of  the  bath  ;  Polishing  the  nickeled  sheets  ,r  ..  *  ....  .  208 


XVI  CONTENTS. 

PAGE 

Nickeling  of  tin-plate,  of  copper  and  brass  sheets,  and  of  sheet  iron  and 

sheet  steel '         .         .         . '       .        .         .209 

Nickeling  of  wire          '. 210 

Apparatus  for  nickeling  wire;  Nickeling  wire  gauze          .         .         .         .  212 
Nickeling  of  knife-blades,  sharp  surgical  instruments,  etc.       .         .         .  213 

Nickeling  of  electrotypes,  cliches,  etc 214 

Baths  for  hard  nickeling .         .  215 

Treatment  of  the  nickeled  plates;  Recovery  of  nickel  from  old  baths      .  210 
Urquhart's  plan  for  recovering  nickel  from  old  solutions ;  To  improve 
defective  nickeling;    Arrangement  of  the   "doctor ;:'    Nickeling  by 
contact  and  boiling .         .         .         .         .         .         ...  .  217 

Deposition  of  an  alloy  containing  nickel  according  to  R.  Kaiser ;   De- 
posits of  nickel  alloys       .         .  .         .         .         .         .         .         .  219 

Nickel  Bronze  ;  French  process  for  the  deposition  of  German  silver ; 
Watt's  method .220 

2.    COBAI/TING. 

Properties  of  cobalt 221 

Baths  for  cobalting  ;  Cobalting  of  copper  plates  for  printing  ;  Determin- 
ation of  the  quantity  of  copper  dissolved  in  stripping  the  cobalt  de- 
posit from  cobalted  copper  plates  ........  222 

Warren's  cobalt  solution  ;  Cobalt  solution  recommended  by  Mr.  G.  W. 
Beardslee,  of  Brooklyn,  N.  Y. ;  R.  Daub's  bath  for  cobalting  small 
fancy  articles 223 

Cobalting  by  contact 224 

CHAPTER  VIII. 

DEPOSITION  OF  COPPER,  BRASS  AND  BRONZE. 
i.  COPPERING. 

Properties  of  copper;  Copper  baths,  their  composition,  preparation,  prop- 
erties and  treatment        ..........  225 

Hassauer's  copper  bath;  Copper  baths  for  iron  and  steel  articles    .         .  226 
Baths  for  coppering  zinc  articles         ........  228 

Baths  prepared  with  cupron  and  cuproso-cupric  sulphite;  Copper  baths 

without  potassium  cyanide 229 

Weil's  copper  bath  and  method  of  coppering;  Copper  bath  recommended 
by  Walenn;  Copper  bath  according  to  Pfanhauser         ....  230 

Gauduin's  copper  bath;  Execution  of  coppering;  Anodes  used;  Forma- 
tion of  slime  on  the  anodes ;  Phenomena  appearing  in  copper  baths 
containing  cyanide  ..........  231 

Necessity  of  careful  cleaning  and  pickling  the  articles  before  coppering.  232 
Preliminary  scouring  and  pickling;  Scratch-brushing  and  treatment  of 
defective  places        ...........  233 


CONTENTS.  xvii 


Prevention  of  the  formation  of  stains  ;  Schultz's  patent  to  prevent  the 
formation  of  stains;  Polishing  the  deposit  of  copper  ....  234 

Treatment  of  coppered  objects  to  be  coated  with  another  metal;  Copper- 
ing small  articles  en  masse;  Coppering  by  contact  and  dipping  .  .  235 

To  coat  zinc  plates  with  a  very  thin  but  hard  layer  of  copper ;  Bacco's 
copper  bath;  Brush-coppering  .  .  .' 236 

Application  of  a  thin  film  of  copper  to  iron  and  steel  objects;  Coppering 
steel  pens,  needles'  eyes,  etc. ;  Inlaying  of  depressions  of  copper  art- 
castings  .  .  .  ..........  .  .  .  .  237 

2.  BRASSING  (CUIVRE-POU  DEPOSIT). 

Constitution  and  varieties  of  brass;  Brass  baths,  their  composition,  pre- 
paration and  treatment  .  .'.__•». 238 

Rules  for  baths  containing  more  than  one  metal  in  solution;  Brass  bath 
according  to  Roseleur  .  .  .  .  .  .  .  .  .  «•  .  239 

Irregular  working  of  fresh  brass  baths;  Bffect  of  an  addition  of  arsenious 
acid  to  brass  baths  .  .  ....  .  .  .  .  .  .  240 

Baths  for  brassing  iron;  Baths  with  cuproso-cupric  sulphite     .         .         .  241 

Bath  for  brassing  cast  iron,  wrought  iron  and  steel  ;  Composition  of  a 
solution  for  transferring  any  copper-zinc  alloy  serving  as  anode  .  242 

Bath  for  brassing  all  kinds  of  metal  recommended  by  Pfanhauser;  Ex- 
ecution of  brassing  ....  .  .  -  .  .'."..  .  243 

On  what  the  color  of  the  deposits  depends;  Anodes  used  and  anode-sur- 
face required  .  ,  .  .  .  .  .  .  ...  .  244 

Formation  of  slime  on  the  anodes,  and  what  it  indicates;  Remedies  for 
the  slow  formation  of  the  deposit  .  .  .  .  .  .  ,  .  245 

Importance  of  the  distance  of  the  objects  to  be  brassed  from  the  anodes; 
Brassing  of  unground  iron  castings  .  ,  fc  .  .  .  .  246 

Brassing  by  contact  and  dipping        .         .        .         .         .  .       /        .         .  247 

3.    BRONZING. 

Gountier's  solution  for  coating  wrought  and  cast  iron  with  bronze;  Other 

bronze  baths  and  their  composition,  preparation  and  treatment  .         .  247 
Hess's  bath  for  deposits  of  tombac;  Execution  of  bronzing     .         .         .  248 

CHAPTER    IX. 
DEPOSITION  OF  SILVER. 

Properties  of  silver  ;  Silver  baths,  their  composition,  preparation  and 
treatment;  Silver  bath  for  a  heavy  electro-deposit  of  silver  (silvering 
by  weight);  Preparation  of  bath  with  silver  chloride  ....  249 

Preparation  of  bath  with  silver  cyanide     .     •    .    -    <        .        ,        .         .  250 

Silver  bath  for  ordinary  electro-silvering;  Treatment  of  the  silver  baths; 
The  silver  anodes^  .....  .  .  .  ...  .  251 

Most  suitable  current-strength  for  silver   baths;  Coupling  of  the  ele- 


xviii  CONTENTS. 

PAGE 

ments;  Indication  of  the  presence  of  too  much  or  not  enough  potas- 
sium cyanide  .  .  ;  .  .  .  .  .  .  .  .  .  .  252 

Objections  to  insoluble  platinum  anodes;  The  behavior  and  appearance 
of  the  anodes  as  criteria  of  the  content  of  potassium  cyanide  in  the 
bath  .  .... 253 

Keeping  the  bath  constant  by  silver  anodes;  Proper  treatment  of  baths 
made  with  chloride  of  silver 254 

Gradual  thickening  of  the  bath;  Augmentation  of  the  content  of  silver 
in  baths  .  .  .  »  . 255 

Determination  of  the  content  in  proper  proportions  of  silver  and  excess 
of  potassium  cyanide  .  .  .  .  .  .  .  .  .  .  256 

Contrivances  to  keep  the  objects  to  be  silvered  in  gentle  motion  while  in 
the  bath 257 

Singular  phenomenon  in  silvering;  Remedy  against  a  yellow  tone  of  the 
silvering  .  ......  .  .  .  .  .  .  .  258 

Areas  silvering  as  introduced  by  the  London  Metallurgical  Co. ;  Experi- 
ments in  areas  silvering  ..........  259 

Execution  of  silvering;  Silvering  by  weight       ......  260 

Mechanical  and  chemical  preparation  of  the  objects;  Treatment  of 
copper  and  its  alloys;  German  silver  and  brass;  Freeing  from  grease; 
Pickling  ;  Rubbing  ;  Pickling  in  the  preliminary  pickle ;  Amalgama- 
ting (quicking)  ...........  261 

Slinging  wires;  Treatment  of  the  objects  while  being  silvered;  Amount 
of  silver  deposited  upon  various  grades  of  plated  ware  manufactured 
by  the  William  Rogers  Manufacturing  Co.,  of  Hartford,  Conn.  .  .  262 

Method  of  controlling  the  weight  of  the  deposit        .         .         .         .         .  263 

Roseleur's  plating  balance  .........  264 

Plating  balance  together  with  the  resistance  board,  voltmeter  and  silver 
bath  ..-. 266 

Treatment  of  articles  which  are  to  retain  the  crystalline  dead  white, 
with  which  they  come  from  the  bath;  Polishing  the  silvered  articles; 
Operation  of  burnishing;  Burnishing  machines  .....  267 

Ordinary  silvering;  Practice  of  the  Meriden  Britannia  Co.'s  works  at 
Meriden,  Conn.,  with  Britannia  or  white  metal 268 

Treatment  of  German  silver  or  nickel  articles  and  of  steel  articles; 
Methods  in  use  with  the  William  Rogers  Manufacturing  Co.,  Hart- 
ford, Conn.,  for  preparing  work  for  plating;  For  cleansing  (steel) 
cntlery;  Nickel-silver  (German  silver)  for  spoons;  Britannia  metal 
(hollow  ware) 269 

Rogers'  striking  solution  ;  Meriden  Company's  striking  solution; 
Methods  of  depositing  an  extra  heavy  coating  of  silver  on  the  convex 
surfaces  of  spoons  and  forks;  "  Stopping  off " 270 

Stopping  of  varnish;  Silvering  by  contact,  by  immersion,  and  cold 
silvering  with  paste;  Bath  for  silvering  by  contact  with  zinc;  Baths 
for  silvering  by  immersion  .........  271 


CONTENTS.  XIX 


Preparation  of  solution  of  sodium  sulphide  .  •  ,  .  .  .  .  272 
Dr.  Ebermayer's  bath  for  immersion  .  ,  .  .  .  .  274 

Silvering  articles,  especially  of  alloys  of  copper  without  the  use  of  a 

current       .         .         ........        .....         .        .         .  275 

Coating  small  articles  such  as  hooks  and  eyes,  pins,  etc.,  with  a  thin 

film  of  silver     .  !  .        .        .         .        .       • .         .         .         .  276 

Cold  silvering  with  paste;  Composition  of  argentiferous  pastes;  Graining  277 
Preparations  used  for  graining   .         .         .         .         .         .         .         .         .  278 

The  operation  of  graining;  Resist  and  its  composition      ....  279 

Gilding  of  grained  watch  parts;  Silvering  of  fine  copper  wire  .  .  280 
Incrustations  with  silver,  gold  and  other  metals  ;  Imitation  of  niel  or 

nielled  silvering;  Preparation  of  the  nielling  powder  ....  281 
Imitation  of  uiel  by  electro-deposition;  Old  (antique)  silvering  .  .  282 
Oxidized  silver  ;  Yellow  color  on  silvered  articles  ;  Stripping  silvered 

articles 283 

Determination  of  electro-deposited  silvering  ^  284 

Method  for  the  determination  of  genuine  silvering  used  by  custom-house 

officers  in  Germany;  Recovery  of  silver  from  old  silver  baths,  etc.  .  285 
The  wet  method;  Reduction  of  the  chloride  of  silver  by  pure  zinc  .  .  286 

CHAPTER  X. 
DEPOSITION  OF  Goux 

Occurrence  and  properties  of  gold  ;  General  composition  of  the  native 

metal ..'...        .        .287 

Shell-gold  or  painter's  gold;  Gold  baths,  their  composition,  preparation 
and  properties  ............  288 

Bath  for  cold  gilding .         .  289 

Bath  with  yellow  prussiate  of  potash  for  cold  gilding       .         .         .         .  290 

Baths  for  hot  gilding .        .  291 

Preparation  of  the  gold  bath  with  the  assistance  of  the  electric  current.  292 
Management  of  gold  baths;  Use*  of  platinum  anodes  for  coloring  the  de- 
posit; Coloration  by  means  of  the  resistance  board  .  293 
Vats  for  gold  baths;  Porcelain  dish  for  small  gold  baths  for  hot  gilding.  294 
Heating  larger  baths;  Execution  of  gilding;  Gilding  without  a  battery.  295 
Preparation  of  the  articles  for  gilding;  Current-strength  for  gilding  .  296 
Gilding  the  inner  surfaces  of  hollow-ware  ;  Gilding  in  the  cold  bath  ; 

Gilding  with  the  hot  bath        . .297 

Red  gilding          .         .        .         ^ 298 

Determination  of  the  content  of  copper  required  for  obtaining  a  beauti- 
ful red  color;  Green  gilding;  Rose-color  gilding;     Dead  gilding.         .  299 
Dead  gilding  on  zinc   .         .         .        .        .     -  .         .         .        .        .         .  300 

Coloring  of  the  gilding;  Gilder's  wax  and  its  preparation        .         .         .  301 
Processes  for  giving  gilded  articles  a  beautiful  rich  appearance  ;  Mode 
of  improving  bad  tones  of  gilding  ...         .         .         .        .         .  302 


XX  CONTENTS. 

PAGE 

Incrustations  with  gold  ;  Gilding  of  metallic  wire   and  gauze;  J.  W. 

Spaeth's  machine  for  gilding  wire  and  gauze  .....  303 
Gilding  by  contact,  by  immersion  and  by  friction;  Baths  for  gilding  by 

contact 305 

Porcelain  capsules  for  dissolving  gold        .......  306 

Preparation  of  "  matt  "  for  gilded  articles;  Baths  for  gilding  by  dipping.  308 
Gilding  of  porcelain,  glass,  etc.;  Gilding  by  friction,  or  gilding  with 
the  rag,  with  the  thumb,  with  the  cork  .         .         .         .         .         .         .  310 

Martin  and  Peyraud's  method  of  gilding  by  friction          ....  311 

Fire  or  mercury  gilding;  Preparation  of  the  gold  amalgam;  Application 

of  the  amalgam .         .         .         .         .  312 

Method  of  gilding  which  is  a  combination  of  fire-gilding  with  electro- 
deposition         .         .         .         .        .        .         .        .        *        .         .         .  314 

Improvement  of  old  dead  gilding;  Du  Fresne's  method  of  gilding;  Re- 
moving gold  from  gilded  articles — "stripping" 315 

Determination  of  genuine  gilding      .       '.         ....        .  x     .         .  316 

Recovery  of  gold  from  gold  baths,  etc. ;  The  wet  process  .  .  .317 
Recovery  of  gold  from  acid  mixtures  .  .  -...,-  .  .  .  .  318 

CHAPTER  XI. 

DEPOSITION  OF  PLATINUM  AND  PALLADIUM. 
I.    DEPOSITION  OF  PLATINUM. 

Properties  of  platinum        .        .        .        .         .  .         .  •"     .         .318 

Platinum  baths,  their  composition,  preparation  and  properties ;  Boett- 

ger's  bath;  Preparation  of  platoso-ammonium  chloride  .  .  .319 
Platinum  bath  patented  by  the  Bright  Platinum  Plating  Co.  of  London; 

Directions  for  preparing  platinum  baths,  by  Dr.  W.  H.  Wahl;  Alkaline 

platinate  bath .  .320 

Preparation  of  an  oxalate  solution  ...  .x  ....  321 
Preparation  of  the  phosphate  bath  ;  Management  of  platinum  baths  .  322 
Execution  of  platinizing  ;  Platinizing  of  large  objects  ;  Production  of 

heavy  deposits ............  323 

Platinizing  of  glass ;  Platinizing  by  contact ;  Recovery  of  platinum 

from  platinum  solutions  .......'...  324 

2.    DEPOSITION  OF  PALLADIUM. 

Properties  of  palladium  ;    Palladium  bath  according  to  M.  Bertrand  ; 
Pilet's  bath  for  plating  watch  movements 325 

CHAPTER  XII. 
DEPOSITION  OF  TIN,  ZINC,  LEAD  AND  IRON. 

I.  DEPOSITION  OF  TIN. 
Properties  of  tin ;  Moire"  metallique  on  tin          .......  326 

Tin  baths,  their  composition,  preparation  and  properties;  Direct  tinning 
of  objects  of  zinc,  copper,  and  brass       .......  327 


CONTENTS.  XXI 


Experiments  with  Salzede's  bronze  bath  ;  Pfanhauser's  experiments ; 
Tin  bath  given  by  Taucher  ...  .  .  .  .  .  .  328 

Management  of  tin  baths  ;  Current  strength  required  ;  Anodes  ;  Choice 
of  tin  salts 329 

Preliminary  treatment  of  iron  and  steel  objects;  Process  of  tinning;  Tin- 
ning by  contact  and  boiling  ;  Solutions  for  tinning  by  contact  .  .  330 

Zilken's  solution  for  tinning  by  contact  in  a  cold  bath;  Tinning  solution 
for  iron  and  steel  articles;  Tinning  solution  for  small  brass  and  copper 
articles 331 

Boettger's  solution  ;  Eisner's  bath  ;  Production  of  a  durable  coating  of 
tin  ;  Tinning  of  needles  . 332 

Superficial  coating  of  tin  on  articles  of  brass,  copper  or  iron  ;  Stalba's 
method  of  tinning  ...........  333 

2.    DEPOSITION  OF  ZINC. 

Properties  of  zinc. 333 

Zinc  baths,  their  composition,  preparation,  and  properties;  Difficulty  In 

producing  a  deposit  of  uniform  thickness  upon  shaped  articles     .         .  334 
Anodes  used  in  zinc  baths  ...........  335 

Execution  of  zincking 336 

Zincking  iron  by  contact ;  To  coat  brass  and  coppar  with  a  bright  layer 
of  zinc;  Zinc  alloys;  Production  of  an  alloy  of  zinc  and  tin  by  the  use 
of  the  battery  .  .  ...  .  .  ,  .  .  «  .  .-  .  337 

3.    DEPOSITION  OF  I,EAD. 

Properties  of  lead;  Lead  baths,  their  composition,  preparation  and  prop- 
erties; Anodes  for  lead  baths 338 

To  coat  gun  barrels  and  other  articles  of  steel  or  iron  with  superoxide  of 
lead;  Leading  by  contact;  Metallic  chromes  (Nobili's  rings)  iridescent 
colors,  electrochromy 339 

Mr.  Gassort's  plan  to  obtain  metallo-chromes    .  .         .        .         .  340 

4.    DEPOSITION  OF  IRON  (STEEUNG). 

Principal  use  of  the  electro-deposition  of  iron ;  Steel  baths,  their  compo- 
sition, preparation,  and  properties;  Varrentrapp's  steel  bath  ;  Boett- 
ger's steel  bath •  ,  .  .  .341 

Baths  for  the  production  of  electrotypes  in  iron  ;  Steel  bath  recom- 
mended by  Klein;  C.  Obernetter's  method  of  steeling  copper  printing 

plates        .         .         .         ..,      .         .         .        . 342 

Production  of  a  deep  black  deposit  of  iron  for  decorative  purposes  .  343 
Management  of  iron  baths;  Execution  of  steeling  .....  344 
Steeling  by  contact *  ...  345 


XX11  CONTENTS. 

PAGE 

CHAPTER  XIII. 

DEPOSITION  OF  ANTIMONY,  ARSENIC,  AIJJMINIUM. 
I.  DEPOSITION  OF  ANTIMONY. 

Properties  of  antimony;  Antimony  baths,  their  composition,  prepara- 
tion and  properties;  Explosive  property  of  the  antimony  deposit         .  345 
Lustrous  non-explosive  deposit  of  antimony      ......  846 

2.    DEPOSITION  OF  ARSENIC. 

Properties  of  arsenic;  Arsenic  baths,  their  composition,  preparation  and 

properties          .        .        . .  346 

Deposits  of  antimony  and  arsenic  by  contact  and  immersion  .         .         .  347 

3.    DEPOSITION   OF   ALUMINIUM. 

Properties  of  aluminium;  Aluminium  baths;  Bertrand's  process;  Goze's 
process  . 348 

Reinhold's  formula;  New  method  for  the  electro -deposition  of  alu- 
minium . 349 

Process  used  by  the  Tacony  Iron  &  Metal  Co.  in  plating  the  columns  of 
the  Philadelphia  Public  Buildings;  Electro-deposition  upon  alu- 
minium .;...........  350 

Advisability  of  previous  coppering,  and  baths  for  that  purpose;  Prof. 
Nees'  process 351 

Electro-deposits  produced  by  the  Mannesmann  Pipe  Works,  Germany  .  352 

CHAPTER  XIV. 

GAI/VANOPI<ASTY  (REPRODUCTION). 

What  is  understood  by  galvanoplasty;  Copper  the  most  suitable  metal 
for  galvauoplastic  purposes  .........  352 

Physical  properties  of  copper  deposited  by  electrolysis;  Smee's  experi- 
ments; Von  Hiibl's  experiments  for  the  determination  of  the  condi- 
tions under  which  deposits  with  different  physical  properties  are  ob- 
tained; Classes  of  processes  used  in  galvanoplasty  ....  353 

I.    GAIVVANOPI,ASTIC   DEPOSITION  IN  THE  CEU,  APPARATUS. 

The  cell  apparatus       ...........  354 

Simple  apparatus  for  amateurs;  Cell  apparatus  for  the  production  of 

cliches 355 

Large  apparatus  ............  356 

French  and  German  forms  of  cell  apparatus     .         .         .         .         .         .  357 

Copper  bath  for  the  cell  apparatus;  Table  of  the  approximate  content 
of  pure  crystallized  blue  vitriol  at  different  degrees  Baume,  and  at 

59°  F 358 

Method  of  removing  an  excess  of  acid  from  the  bath         ....  359 


CONTENTS.  xxiii 


PAGE 
2.    GAI^VANOPIvASTlC  DEPOSITION  BY  THE  BATTERY  AND  DYNAMO-MACHINE. 

Arrangement  for  the  employment  of  external  sources  of  current    .         .  359 
Depositions  with  the  battery;  Use  of  the  Daniell  and  of  Bunsen  elements; 
Coupling  of  elements       ...        .       ......         .         .         .  3GO 

Depositions  with  dynamo- machines  ;  Copper  baths  for  galvanoplastic 
depositions  with  a  separate  source  of  current        .....  361 

Bath  for  depositing  with  the  dynamo;  Bath  for  depositing  with  the  bat- 
tery; Von  Hiibl's  observations  on  the  elasticity,  strength  and  hardness 
of  galvanoplastic  deposits  of  copper;  Most  suitable  solution  for  copper 
printing  plates;  Current-density  for  baths  at  rest  and  in  motion  .         .  362 
Disadvantage  of  the  difference  in  composition  of  the  upper  and  lower 
layers  of  the  bath     .         .         ...         .         .         .         ...  363 

Various  methods  of  effecting  the  agitation  of  the  bath     ....  364 

Anodes  used,  and  their  surfaces  in  proportion  to  that  of  the  cathodes; 
Determination  of  free  acid      .        .        .         .         .         .    •     .         .         .  365 

Determination  of  the  content  of  copper  according  to  Haen      .         .         .  366 
Preparation  of  moulds  (matrices)  in  plastic  material;  Moulding  in  gutta- 
percha      ...         .......         .       -.    .     .         .         .         .  367 

The  toggle  press          ...         .        .     -   .        ...         ...  368 

Hydraulic  press  .         .         .         «         .         .        -»         .         .         .         .         .  369 

Moulding  in  wax  (stearine);  Various  wax  mixtures.         .  :      .        .         .  370 
Preparation  of  the  wax  mould    .         .         .         .         .         .         ....  371 

Black-leading,  and  black-leading  machines ;  Silas  P.  Knight's  process 

of  black-leading .        ...  372 

Preliminary  coating  of  the  black-leaded  surface  with  copper ;  Gilt  and 

silvered  black-lead  .         .         .         .         . 373 

Wiring  the  mould;  The  electric-connection  gripper 374 

Suspension  of  the  moulds  in  the  bath;  Chief  requsite  for  the  production 
of  a  dense,  coherent  and  elastic  deposit ;  Strength  of  the  sulphuric 
acid  for  filling  the  clay  cells  .  .  .  __  .  .  .  .  .  375 

Most  suitable   current-density  for  the  production   of  a  good    deposit; 

Coupling  of  the  elements        .         .'-  .         .         .         .         .  376 

Controlling  the  current  by  the  resistance  board  ;  Time  required  for  a 

sufficiently  heavy  deposit;  Accumulators  and  their  use        ...  377 
Electro-chemical  process  of  forming  storage  batteries;  Diagram  showing 
connections  of  a  plant  as  installed  by  the  Electro-Chemical  Storage 

Battery  Co. ,  of  New  York         . 378 

Detaching  the  deposit  from  the  mould;  Backing  the  deposit  or  shell       .  380 
Finishing;  The  saw  table;  Types  of  power  planing  or  shaving  machines.  382 
Mounting  the  plates ;  Book  plates ;  Process  of  making  a  copy  directly 
from  a  metallic  surface  without  the  interposition  of  wax  or  gutta- 
percha      .....         . 383 

Electro-etching  .         ....'...-... t        .  .       .  385 

Composition  for  etching  ground;  Preparation  of  printing  plates  in  relief.  386 


xxiv  CONTENTS. 

PAGE 

Heliography     .... 387 

Galvanoplastic   reproduction   of  busts,    vases,    etc.;   Materials   for   the 

moulds      .         .         . .388 

Dissection  of  objects;  Moulding  round  articles  in  gutta-percha;  Metallic 

alloys  for  the  preparation  of  moulds 389 

Moulding  with  metallic  alloys ;  Taking  casts  from  metallic  coins  and 
medals  in  plaster  of  Paris        ......         ...  390 

Casts  from  large  plastic  objects  with  undercut  surfaces  and  reliefs  in 

plaster  of  Paris 391 

Making  plaster  of  Paris  moulds  impervious  to  fluids         ....  392 

Making  the  moulds  conductive;  Metallization  by  the  wet  way        .         .  393 
Parke's  and  various  other  methods  of  metallization  by  the  wet  way         .  394 
Metallization  by  metallic  powders     .         .         .         .         .         .         .         .  395 

Ivenoir's  process— galvanoplastic  method  for  originals  in  high  relief; 

Gelatine  moulds,  and  their  preparation 396 

Brandley's  directions  for  preparing  gelatine  moulds  ;  Special  uses  of 
galvanoplasty ;  Nature  printing      ...         .         .         .         .        .  397 

Philipp's  process  for  coating  laces  and  tissues  with  copper,  and  then  sil- 
vering or  gilding  ;  Corvin's  niello  ........  398 

Coating  grasses,  leaves,  flowers,  etc.,  with  copper  and  then  silvering, 
gilding  or  platinizing  ;  Plates  for  the  production  of  imitations  of 
leather  ;  To  coat  wood,  etc.,  with  a  galvanoplastic  deposit  of  copper  .  399 
To  protect  wooden  handles  of  surgical  instruments,  etc.,  from  the  attacks 
of  the  acid  copper  bath  ;  Copper  deposit  for  the  mercury  vessels  of 
thermometers  ;  Metallization  of  glass,  porcelain,  clay,  terra  cotta,  etc. ; 

Galvanoplastic  operations  in  iron 400 

Galvanoplastic  operations  in  nickel  .         .         .         .         .         .         .         .  401 

Galvanoplastic  operations  in  silver  and  gold     ......  402 

Bath  for  galvanoplastic  operations  with  silver  ;  Bath  for  galvanoplastic 
operations  with  gold  .  .  .  .  .  .  .  .  .  .  403 

CHAPTER  XV. 

COLORING,  PATINIZING  ;  OXIDIZING,  ETC.  OF  METALS.— LACQUERING. 

What  is  understood  by  patina  and  patinizing;  Coloring  of  copper;  Shades 
from  the  pale-red  of  copper  to  a  dark  chestnut-brown  ....  403 

Brown  color  upon  copper  ;  Method  used  in  the  Paris  Mint ;  Bronze-like 
color  on  copper  ...  .  .  .  .  .  .  .  .  404 

Red-brown  color  on  copper  ;  To  color  copper  blue-black  ;  Cuivre  fum6; 
Black  color  on  copper  ;  Dead-black  on  copper 405 

Solution  for  obtaining  a  deep  black  color  on  copper;  Imitation  of  genu- 
ine patina 406 

Steel-gray  color  upon  copper  ;  Coloring  copper  dark  steel-gray  ;  Vari- 
ous colors  upon  massive  copper,  brass  and  nickel  ....  407 


CONTENTS.  XXV 


Coloring  of  brasses  and  bronzes;  Lustrous  black  on  brass;  Steel-gray  on 
brass 408 

Gray  color  with  a  bluish  tint  on  brass  ;  Pale  gold  color  on  brass ;  Straw 
color,  to  brown,  through  golden  yellow,  and  tombac  color  on  brass ; 
Color  resembling  gold  on  brass  ........  409 

Brown  color,  called  bronze  Barbedienne,  on  brass ;  Coloring  bronze 
articles  dead-yellow  or  clay-yellow  to  dark  brown  ....  410 

Smoke  bronze  ;  Violet-  and  corn-flower  blue  on  brass  ;  Ebermayer's  ex- 
periments in  coloring  brass  .........  411 

Coloring  zinc  ;  Experiments  in  coloring  zinc  black;  Blue-black  on  zinc; 
Gray  coating  on  zinc  ;  Bronzing  on  zinc  ......  413 

Red-brown  color  on  zinc  ;  Yellow-brown  shades  on  zinc  ;  Coloring  of 
iron  ;  Lustrous  black  on  iron  .........  414 

Meritens's  process  for  obtaining  a  bright  black  color  on  iron  .         .         .  415 

Durable  blue  on  iron  ;  Brown-black  coating  with  bronze  lustre  on  iron  ; 
To  give  iron  a  silvery  appearance  with  high  lustre  ;  Coloring  of  tin  ; 
Bronze-like  patina  on  tin  ;  Durable  and  very  warm  sepia-brown  tone 
upon  tin  and  its  alloys  ;  Dark  coloration  on  tin 416 

Coloring  of  silver  ;  Lacquering  ;  Use  of  lacquers  in  the  electro-plating 
industry  ;  Application  of  lacquers  ;  Cellulose  lacquers  and  varnishes  ; 
Zapon 417 

Kristaline;  Preparation  of  a  lacquer  similar  to  zapon  or  kristaline  .         .418 

Operations  of  gold  varnishers     .         .         .         .         .         .         .         .         .  419 

Varnishes  at  the  disposal  of  gold  varnishers  ;  Resinous  substances  and 
tinctorial  matters  used  in  the  manufacture  of  varnish  ;  Removal  of 
varnish  from  imperfectly  varnished  objects 420 

CHAPTER  XVI. 
HYGIENIC  RUI,ES  FOR  THE  WORKSHOP. 

Neutralization  of  the  action  of  acid  upon  the  enamel  of  the  teeth  and 
the  mucuous  membranes  of  the  mouth  and  throat;  Protection  against 
the  corrosive  effect  of  lime  and  caustic  lyes;  Vessels  used  in  the  estab- 
lishment not  to  be  used  for  drinking  purposes  .....  421 

Precautions  in  handling  potassium  cyanide  and  its  solutions;  Sensitive- 
ness of  many  persons  to  nickel  solutions;  Poisoning  by  hydrocyanic 
(prussic)  acid,  potassium  cyanide,  or  cyanides  .....  422 

Remedies  to  be  applied;  Poisoning  by  copper  salts,  by  lead  salts,  by 
arsenic,  by  alkalies,  by  mercury  salts,  sulphuretted  hydrogen,  and  by 
chlorine,  sulphurous  acid,  nitrous  and  hyponitric  gases,  and  remedies.  423 


XXVI  CONTENTS. 


CHAPTER  XVII. 

CHEMICAL  PRODUCTS  AND  VARIOUS  APPARATUS  AND  INSTRUMENTS  USED 
IN  ELECTRO-PLATING. 

A.  CHEMICAL  PRODUCTS. 

PAGE 

I.  Acids. 

Sulphuric  acid  (oil  of  vitriol)  and  its  recognition      .....  424 
Nitric  acid  (aqua  fortis,  spirit  of  nitre);  Hydrochloric  acid  (muriatic 

acid)  and  their  recognition     .........  425 

Hydrocyanic  acid  (prussic  acid);  Citric  acid;  Boric  acid  (boracic  acid), 

and  their  recognition 426 

Arsenious  acid   (white  arsenic,  arsenic,  ratsbane);  Chromic  acid,   and 

their  recognition 427 

Hydrofluoric  acid  and  its  recognition 428 

II.  Alkalies  and  Alkaline  Earths. 

Potassium  hydrate  (caustic  potash);  Sodium  hydrate  (caustic  soda)         .  428 
Ammonium  hydrate  (ammonia  or  spirits  of  hartshorn),  and  its  recogni- 
tion; Calcium  hydrate  (burnt  or  quick  lime) 429 

III.  Sulphur  Combinations. 

Sulphuretted  hydrogen  (sulphydric  acid,  hydrosulphuric  acid),  and  its 
recognition  ............  429 

Potassium  sulphide  (liver  of  sulphur)  and  its  recognition;  Ammonium 
sulphide  (sulphydrate  or  hydrosulphate  of  ammonia);  Carbon  disul- 
phide  or  bisulphide;  Antimony  sulphide;  Black  sulphide  of  antimony 
(stibium  sulfuratum  nigruwi}\  Red  sulphide  of  antimony  {stibium 
sulfuralum  aurantiacum}  .........  430 

Arsenic  trisulphide  or  arsenious  sulphide  (orpiment);  Ferric  sulphide    .  431 

IV.  Chlorine  Combinations. 

Sodium  chloride  (common  salt,  rock  salt)  and  its  recognition;  Ammon- 
ium chloride  (sal  ammoniac)  and  its  recognition;  Antimony  trichlor- 
ide (butter  of  antimony) 431 

Arsenious  chloride;  Copper  chloride;  Tin  chloride;  Stannous  chloride 
or  tin  salt,  and  its  recognition;  Stannic  chloride;  Zinc  chloride  (hydro- 
chlorate  or  muriate  of  zinc,  butter  of  zinc)  and  its  recognition  .  .  432 

Zinc  chloride  and  ammonium  chloride;  Nickel  chloride,  and  its  recog- 
nition; Cobalt  chloride,  and  its  recognition;  Silver  chloride  (horn  sil- 
ver), and  its  recognition  .  .........  433 

Gold  chloride  (terchloride  of  gold,  muriate  of  gold,  auric  chloride),  and 
its  recognition;  Platinic  chloride  or  hydroplatinic  chloride,  and  its  re- 
cognition .............  434 


CONTENTS.  XXV11 


V.  Cyanides. 

Potassium  cyanide  (white  prussiate  of  potash)         . .        .        .    '    -.        .  435 
Recognition  of  potassium  cyanide;  Comparative  table  of  potassium  cya- 
nide with  a  different  content;  Copper  cyanides,  and  their  recognition.  436 
Zinc  cyanide  (hydrocyanate  of  zinc,  prussiate  of  zinc),  and  its  recogni- 
tion; Silver  cyanide  (prussiate,  or  hydrocyanate  of  silver);  Potassium 
ferro-cyanide  (yellow  prussiate  of  potash),  and  its  recognition     .         .  437 

VI.  Carbonates. 

Potassium  carbonate  (potash)  and  its  recognition ;  Acid  potassium  car- 
bonate or  monopotassic  carbonate,  commonly  called  bicarbonate  of 
potash;  Sodium  carbonate  (washing  soda)  ......  438 

Sodium  bicarbonate  (baking  powder)  ;  Calcium  carbonate  (marble, 
chalk);  Whiting;  Copper  carbonate,  and  its  recognition;  Zinc  car- 
bonate, and  its  recognition  .........  439 

Nickel  carbonate,  and  its  recognition;  Cobalt  carbonate.         .         .         .  440 

* 

VII.  Sulphates  and  Sulphites. 

Sodium  sulphate  (Glauber's  salt);  Ammonium  sulphate,  and  its  recog- 
nition; Aluminium-potassium  sulphate  (potash-alum),  and  its  recog- 
nition .  .  .  .  .  .  .  .  .  .  .  .  440 

Iron  sulphate  (iron  protosulphate,  ferrous  sulphate  or  green  vitriol),  and 
its  recognition;  Iron-ammonium  sulphate;  Copper  sulphate  (cupric 
sulphate  or  blue  vitriol),  and  its  recognition.  .  .  .  .  .  441 

Cuprous  sulphite  ;  Zinc  sulphate  (white  vitriol),  and  its  recognition  ; 
Nickel  sulphate,  and  its  recognition  .  .  .  .  ..  .  .  442 

Nickel-ammonium  sulphate;  Cobalt  sulphate  and  its  recognition;  Cobalt- 
auimoniuni  sulphate;  Sodium  sulphite  and  bisulphite  ....  443 

VIII.  Nitrates. 
Potassium  nitrate  (saltpetre,  nitre),  and  its  recognition;  Sodium  nitrate 

(cubic  nitre  or  Chile  saltpetre);  Mercurous  nitrate        .         .         .         .444 
Mercuric  nitrate,  and  its  recognition;  Silver  nitrate  (lunar  caustic),  and 

its  recognition          .         .        .         .    —  .        .....         .         .         .  445 

IX.  Phosphates  and  Pyrophosphates. 

Sodium  phosphate,  and  its  recognition;  Sodium  pyrophosphate,  and  its 
recognition;  Ammonium  phosphate  .  .  .  .-  .  .  .  446 

X.  Salts  of  the  Organic  Acids. 

Potassium  bitartrate  (cream  of  tartar) »         .  446 

Potassium  sodium  tartrate  (Rochelle  or  Seignette  salt),  and  its  recogni- 
tion; Antimony-potassium  tartrate  (tartar  emetic),  and  its  recognition; 
Copper  acetate  (verdigris);  Lead  acetate  (sugar  of  lead),  and  its  re- 
cognition .         .         .        ,        .r  •    .         .         .         .         .         .         .         .  447 

Sodium  citrate    .        .         .         .         «        .        .         .         .  .  448 


XXVlii  CONTENTS. 

PAGE 
B.    VARIOUS  APPARATUS  AND  INSTRUMENTS. 

Glass  balloons  and  flasks;  Evaporating  dishes  or  capsules;  Glass  jars    .  448 

Crucibles  ;  Hydrometers    .  449 

Table  showing  readings  of  different  hydrometers      .....  450 

Filters .451 

Siphons        .         .         .        .         .         . 452 

Stirring  rods        ............  453 


APPENDIX. 

Check  voltmeter 454 

The  Bossard  mechano-electroplating  tanks  ;  The  long  tank     .         .         .  455 
Manipulation  of  the  long  tank  .         .        .         .  .         .        .         .  456 

The  circular  tank         ...........  457 

Advantages  claimed  for  the  mechano-electroplating  tanks       .         .         .  460 
Useful  tables ;  Table  of  elements  with  their  symbols,  atomic  weights, 
and  specific  gravities        .         ....        .  .         .         .         .  461 

Table  of  chemical  and  electro-chemical  equivalents;  Explanation  of  the 

table          .        .        ... 462 

Table  showing  the  value  of  equal  current  volumes  as  expressed  in  am- 
peres per  square  decimetre,  per  square  foot  and  per  square  inch  of 
electrode  surface      .        .         .        ...         .         .         .         .         .  463 

Explanation  of  the  table  ;  Table  showing  the  specific  electric  resistances 
of  different  sulphuric  acid  solutions  of  various  temperatures  ;  Table 
showing  the  specific  electric  resistances  of  different  copper  sulphate 

solutions  at  various  temperatures 464 

Table  of  electro-motive  force  of  elements 465 

Table  showing  the  solubility  of  various  substances  ;  Table  showing  the 

composition  of  the  most  usual  alloys  and  solders 466 

Alloys .        .         .        . 467 

Solders ;  Hard  solder ;  Silver  solder .         .         .         .         .         .        .         .468 

Gold  solder;  Table  of  melting  points  of  some  metals;  Table  of  high 
temperatures  ;  Table  of  the  specific  gravity  and  content  of  solutions 
of  potassium  carbonate  at  57.2°  F.  .......  469 

Table  showing  the  specific  gravity  of  sulphuric  acid  at  59°  F.  .         .  470 

Table  of  specific  gravity  and  content  of  nitric  acid  ;  Table  showing  the 
specific  gravity  of  sal  ammoniac  solutions  at  66.2°  F.    ....  471 

Table  showing  the  electrical  resistance  of  pure  copper  wire  of  various 
diameters ;  Resistance  and  conductivity  of  pure  copper  at  different 

temperatures 472 

Table  showing  actual  diameters  in  decimal  parts  of  an  inch  correspond- 
ing to  the  numbers  of  various  wire  gauges  ......  473 


CONTENTS.  XXIX 

PAGE 

Weight  of  iron,  copper,  and  brass  wire  and  plates 474 

Rules  for  speed  ;  To  find  speed  of  countershaft  in  accordance  with  main 
shaft  and  machine;  Example;  To  find  diameter  of  pulley  on  the  main 
shaft ;  Example  ;  To  find  diameter  of  pulley  on  counter-shaft  carry- 
ing belt  to  machine  ;  Example  ;  To  find  the  speed  of  a  machine  .  475 

Comparison  of  the  scales  of  the  Fahrenheit,  Centigrade,  and  Reaumur 
thermometers,  and  rules  for  converting  one  scale  into  another  .  .  476 

Index .         .  .  477 


ELECTRO-DEPOSITION  OF  METALS. 


L 

HISTORICAL    PART. 


CHAPTER  I. 

HISTORICAL   REVIEW   OF   ELECTRO-METALLURGY. 

IN  reviewing  the  history  of  the  development  of  electrolysis, 
i.  e.y  the  reduction  of  a  metal  or  a  metallic  alloy  from  the  solu- 
tion of  its  salts  by  the  electric  current,  the  simple  reduction 
which  takes  place  by  the  immersion  of  one  metal  in  the  solution 
of  another,  may  be  omitted.  This  mode  of  reduction  was  well 
known  to  the  alchemist  Zozimus,  who  described  the  reduction  of 
copper  from  its  solutions  by  means  of  iron,  while  Paracelsus 
speaks  of  coating  copper  and  iron  with  silver  by  simple  immer- 
sion in  a  solution  of  silver. 

Before  the  discovery,  in  1789,  of  contact-electricity  by  Luigi 
Galvani,  there  was  nothing  like  a  scientific  reduction  of  metal 
by  electricity;  and  only  in  1799  did  Alexander  Volta,  of 
Pavia,  succeed  in  finding  the  true  causes  of  Galvani's  discovery. 
Galvani  observed  while  dissecting  a  frog  on  a  table,  whereon 
stood  an  electric  machine,  that  the  limbs  suddenly  became  con- 
vulsed by  one  of  his  pupils'  touching  the  crural  nerve  with  the 
dissecting-knife  at  the  instant  of  taking  a  spark  from  the  con- 
ductor of  the  machine.  The  experiment  was  several  times 
repeated,  and  it  was  found  to  answer  in  all  cases  when  a  metallic 


2  ELECTRO-DEPOSITION    OF   METALS. 

conductor  was  connected  with  the  nerve,  but  not  otherwise.  He 
observed  that  muscular  contractions  were  produced  by  forming 
a  connection  between  two  different  metals,  one  of  which  was 
applied  to  the  nerve,  and  the  other  to  the  muscles  of  the  leg. 
Similar  phenomena  having  been  found  to  arise  when  the  leg  of 
the  frog  was  connected  with  the  electric  machine,  it  could 
scarcely  be  doubted  that  in  both  cases  the  muscular  contrac- 
tions were  produced  by  the  same  agent.  From  a  course  of 
experiments,  Galvani  drew  the  erroneous  inference  that  these 
muscular  contractions  were  caused  by  a  fluid  having  its  seat  in 
the  nerves,  which  through  the  metallic  connections  flowed  over 
upon  the  muscles.  Everywhere,  in  Germany,  England  and 
France,  eminent  scientists  hastened  to  repeat  Galvani's  experi- 
ments, in  the  hope  of  discovering  in  the  organism  a  fluid  which 
they  considered  the  vital  principle  ;  but  it  was  reserved  to  Volta 
to  throw  light  upon  the  prevailing  darkness.  In  his  repeated 
experiments  this  eminent  philosopher  observed  that  one  cir- 
cumstance had  been  entirely  overlooked,  namely,  that  in  order 
to  produce  strong  muscular  contractions  in  the  frog-leg  experi- 
ment it  was  absolutely  necessary  for  the  metallic  connection  to 
consist  of  two  different  metals  coming  in  contact  with  each 
other.  From  this  he  drew  the  inference  that  the  agent  pro- 
ducing the  muscular  contractions  was  not  a  nerve-fluid,  but  was 
developed  by  the  contact  of  dissimilar  metals,  and  identical 
with  the  electricity  of  the  electric  machine. 

This  discovery  led  to  the  construction  of  what  is  known  as 
the  pile  of  Volta,  or  the  voltaic  pile.  The  same  philosopher 
found  that  the  development  of  electricity  could  be  increased  by 
building  up  in  regular  order  a  pile  of  pairs  of  plates  of  dissimi- 
lar metals,  each  pair  being  separated  on  either  side  from  the 
adjacent  pairs  by  pieces  of  moistened  card-board  or  felt.  On 
account  of  various  defects  of  the  voltaic  pile,  Cruikshank  soon 
afterwards  devised  his  well-known  trough  battery,  which  con- 
sisted of  square  plates  of  copper  and  zinc  soldered  together, 
and  so  arranged  and  fastened  in  parallel  order  in  a  wooden  box, 
that  between  each  pair  of  plates  a  sort  of  trough  was  formed, 
which  was  filled  with  acidulated  water. 


HISTORICAL   REVIEW   OF   ELECTRO-METALLURGY.  3 

Nicholson  and  Carlisle,  on  May  2,  1800,  first  decomposed 
water  into  hydrogen  and  oxygen  by  electrolysis ;  and,  in  1801, 
Wollaston  found  that  if  a  piece  of  silver  in  connection  with  a 
more  positive  metal,  for  instance,  zinc,  be  put  into  a  solution  of 
copper,  the  silver  will  be  coated  over  with  copper,  which  coat- 
ing will  stand  the  operation  of  burnishing. 

Cruikshank,  in  1803,  investigated  the  behavior  of  solutions 
of  nitrate  of  silver,  sulphate  of  copper,  acetate  of  lead,  and  sev- 
eral other  metallic  salts,  towards  the  galvanic  current,  and  found 
that  the  metals  were  so  completely  reduced  from  their  solutions 
by  the  current  as  to  suggest  to  him  the  analysis  of  minerals  by 
means  of  the  electric  current. 

To  Brugnatelli  we  owe  the  first  practical  results  in  electro- 
gilding.  In  1805,  he  gilded  two  silver  medals  by  connecting 
them  by  means  of  copper  wire  with  the  negative  pole  of  the 
pile,  and  allowing  them  to  dip  in  a  solution  of  fulminating  gold 
in  potassium  cyanide,  while  a  piece  of  metal  was  suspended  in 
the  solution  from  the  positive  pole.  He  also  observed  that  the 
positive  plate,  if  it  consisted  of  an  oxidizable  metal,  was  dis- 
solved. 

One  of  the  greatest  discoveries  connected  with  the  subject, 
however,  is  that  of  Sir  Humphry  Davy,  made  October  6,  1807, 
when,  by  the  decomposition  of  the  alkalies  by  means  of  the 
electric  current,  he  discovered  the  metals  potassium  and  sodium. 

Prof.  Oersted,  of  Copenhagen,  in  1820,  found  that  the  mag- 
netic needle  is  deflected  from  its  direction  by  the  electric  cur- 
rent. It  was  known  long  before  this  that  powerful  electric  dis- 
charges affect  the  magnetic  needle ;  it  had,  for  instance,  been 
observed  that  the  needle  of  a  ship's  compass  struck  by  light- 
ning had  lost  its  property  of  indicating  the  North  Pole,  and 
several  physicists,  among  them  Franklin,  had  succeeded  in  pro- 
ducing the  same  phenomena  by  heavy  discharges  of  the  elec- 
trical machine,  but  they  were  satisfied  with  the  supposition  that 
the  electric  current  acted  mechanically,  like  the  blow  of  a 
hammer.  Oersted  first  perceived  that  electricity  must  be  in  a 
state  of  motion  in  order  to  act  upon  magnetism.  This  led  to 


4  ELECTRO-DEPOSITION    OF   METALS. 

the  construction  of  the  galvanoscope  or  galvanometer,  an  in- 
strument which  indicates  whether  the  elements  or  other  source 
of  current  furnish  a  current  or  not,  and  by  which  the  intensity 
of  the  source  of  current  may  also  to  a  certain  degree  be  recog- 
nized. 

Ohm,  in  1827,  discovered  the  law  named  after  him,  that  the 
strength  of  a  continuous  current  is  directly  proportional  to  the 
difference  of  potential  or  electro-motive  force  in  the  circuit,  and 
inversely  proportioned  to  the  resistance  of  the  circuit.  This  law 
will  be  more  fully  discussed  in  the  theoretical  part. 

Ohm's  discovery  was  succeeded,  in  1831,  by  the  important 
discovery  of  electric  induction  by  Faraday.  By  induction  is  un- 
derstood the  production  of  an  electric  current  in  a  closed  circuit 
which  is  in  the  immediate  neighborhood  of  a  current-carrying 
wire.  Faraday  further  found  that  the  current  induced  in  the 
neighboring  wire  is  not  constant,  because  after  a  few  oscilia- 
tions  the  magnetic  needle  returned  to  the  position  occupied  by 
it  before  a  current  was  passed  through  the  current-carrying 
wire ;  whilst  when  the  current  was  broken  the  needle  deflected 
in  the  opposite  direction. 

In  the  year  following  the  discovery  of  Faraday,  Pixii,  of 
Paris,  constructed  the  first  electro-magnetic  induction  machine. 

Faraday's  electrolytic  law  of  the  proportionality  of  the  cur- 
rent-strength and  its  chemical  action,  and  that  the  quantities  of 
the  various  substances  which  are  reduced  from  their  combina- 
tions by  the  same  current  are  proportional  to  their  chemical 
equivalents,  was  laid  down  and  proved  in  1833,  and  upon  this 
Faraday  based  the  measurement  of  the  current-strength  by 
chemical  deposition,  as,  for  instance,  that  of  water,  in  the 
voltmeter. 

Of  the  practical  electro-chemical  discoveries  there  remain  to 
be  mentioned  the  production  of  iridescent  colors,  in  1826,  by 
Nobili,  and  the  production  of  the  amalgams  of  potassium  and 
sodium,  in  1853,  by  Bird. 

The  actual  galvanoplastic  process,  however,  dates  from  the 
year  1838.  In  the  spring  of  1838,  Prof.  Jacoby  announced  to 


HISTORICAL   REVIEW   OF   ELECTRO-METALLURGY.  5 

the  Academy  of  Sciences  of  St.  Petersburg,  a  description  of  his 
discovery  of  the  utility  of  galvanic  electricity  as  a  means  of  re- 
producing objects  of  metal.  Hence  Jacoby  must  be  considered 
the  father  of  galvanoplasty  in  as  far  as  he  was  the  first  to  utilize 
and  give  practical  form  to  the  discoveries  made  up  to  that  time. 
Though  Jacoby's  process  was  published  in  the  English  periodi- 
cal, "The  Athenaeum/'  of  May  4,  1839,  Mr.  T.  Spencer,  who 
read  a  paper  on  the  same  subject,  September  13,1 839,  before  the 
Liverpool  Polytechnic  Society,  claimed  priority  of  invention,  as 
was  also  done  by  Mr.  C.  J.  Jordan,  who,  on  May  22,  1839,  sent 
a  letter  to  the  "  London  Mechanical  Magazine,"  which  was  pub- 
lished on  June  8,  1839. 

From  this  time  forward  the  galvanoplastic  art  made  rapid 
progress,  and  by  the  skill  and  enterprise  of  such  men  as  the 
Elkingtons,  of  Birmingham,  and  De  Ruolz,  of  Paris,  it  was 
speedily  added  to  the  industrial  arts. 

Though  copies  of  a  metallic  object  by  means  of  galvanoplasty 
could  now  be  made,  the  employment  of  the  process  was  re- 
stricted to  metallic  objects  of  a  form  suitable  for  the  purpose, 
until,  in  1840,  Murray  succeeded  in  making  non-metallic  sur- 
faces conductive  by  the  application  of  graphite  (black  lead, 
plumbago),  which  rendered  the  production  of  galvanoplastic 
copies  of  wood-cuts,  plaster-of-Paris  casts,  etc.,  possible. 

Dr.  Montgomery,  in  1843,  sent  to  England  samples  of  gutta- 
percha,  which  was  soon  found  to  be  a  suitable  material  for  the 
production  of  negatives  of  the  original  models  to  be  reproduced 
by  galvanoplasty. 

Though  it  was  now  understood  how  to  produce  heavy  de- 
posits of  copper,  those  of  gold  and  silver  could  only  be  obtained 
in  very  thin  layers,  Scheele's  observations  on  the  solubility  of 
the  cyynide  combinations  of  gold  and  silver  in  potassium 
cyanide,  led  Wright,  a  co-worker  of  the  Elkingtons,  to  employ, 
in  1840,  such  solutions  for  the  deposition  of  gold  and  silver, 
and  it  was  found  that  deposits  produced  from  these  solutions 
could  be  developed  to  any  desired  thickness.  The  use  of  solu- 
tions of  metallic  cyanides  in  potassium  cyanide  prevails  at  the 


6  ELECTRO-DEPOSITION    OF   METALS. 

present  time,  and  the  results  obtained  thereby  have  not  been 
surpassed  by  any  other  practice. 

From  the  same  year  also  dates  the  patent  for  the  deposition 
of  nickel  from  solution  of  nitrate  of  nickel,  which,  however,  did 
not  attract  any  special  attention.  This  may  have  been  chiefly 
due  to  the  fact  that  the  deposition  of  nickel  from  its  nitrate 
solution  is  the  most  imperfect  and  the  least  suitable  for  the 
practice. 

To  Mr.  Alfred  Smee  we  owe  many  discoveries  in  the  deposi- 
tion of  antimony,  platinum,  gold,  silver,  iron,  lead,  copper,  and 
zinc.  In  publishing  his  experiments,  in  1841,  he  originated 
the  very  appropriate  term  "electro-metallurgy"  for  the  process 
of  working  in  metals  by  means  of  electrolysis. 

Prof.  Bcettger,  in  1842,  pointed  out  that  dense  and  lustrous 
depositions  of  nickel  could  be  obtained  from  its  double  salt, 
sulphate  of  nickel  with  sulphate  of  ammonium,  as  well  as  from 
ammoniacal  solution  of  sulphate  of  nickel ;  and  that  such  de- 
posits, on  account  of  their  slight  oxidability,  great  hardness, 
and  elegant  appearance,  were  capable  of  many  applications. 
However,  Bcettger' s  statements  fell  into  oblivion,  and  only  in 
later  years,  when  the  execution  of  nickeling  was  practically 
taken  up  in  the  United  States,  his  labors  in  this  department 
were  remembered  in  Germany.  To  Bcettger  we  are  also  in- 
debted for  directions  for  coating  metals  with  iron,  cobalt, 
platinum,  and  various  patinas. 

In  the  same  year,  De  Ruolz  first  succeeded  in  depositing 
metallic  alloys — for  instance,  brass — from  the  solutions  of  the 
mixed  metallic  salts.  In  1843  the  first  use  of  thermo-electricity 
appears  to  have  been  made  by  Moses  Poole,  who  took  out  a 
patent  for  the  use  of  a  thermo-electric  pile  instead  of  a  voltaic 
battery  for  depositing  purposes. 

From  this  time  forward  innumerable  improvements  in  exist- 
ing processes  were  made ;  and  also  the  first  endeavors  to  apply 
Faraday's  discoveries  to  practical  purposes. 

The  invention  of  depositing  metals  by  means  of  a  permanent 
current  of  electricity  obtained  from  steel  magnets  was  perfected 

. 


HISTORICAL    REVIEW    OF    ELECTRO-METALLURGY.  *] 

and  first  successfully  worked  by  Messrs.  Prime  &  Son,  at  their 
large  silverware  works,  Birmingham,  England,  and  the  original 
machine,  constructed  by  Woolrych  in  1844 — the  first  magnetic 
machine  that  ever  deposited  silver  on  a  practical  scale — is  still 
preserved  at  their  works  in  its  original  position  as  a  valuable  and 
interesting  relic.  The  Woolrych  machine  stands  5  feet  high,  5 
feet  long,  and  2^  feet  wide.  An  illustration  of  this  original 
electro-plating  machine,  kindly  furnished  us  by  the  Hanson  & 
Van  Winkle  Co.,  of  Newark,  N.  J.,  is  given  in  Fig.  I. 


FIG.  i. 


As  early  as  1854,  Christofle  &  Co.  endeavored  to  replace  their 
batteries  by  magneto-electrical  machines,  and  used  the  Holmes 
type,  better  known  as  the  Alliance  Machine,  which,  however,  did 
not  prove  satisfactory ;  and  besides,  the  prices  of  these  machines 
were  in  comparison  with  their  efficacy  exorbitant.  The  ma- 


8  ELECTRO-DEPOSITION    OF   METALS. 

chine  constructed  by  Wilde  proved  objectionable  on  account  of 
its  heating  while  working,  and  the  consequent  frequent  inter- 
ruptions in  the  operations. 

In  1860  Dr.  Antonie  Pacinotti,  of  Pisa,  suggested  the  use  of 
an  iron  ring  wound  round  with  insulated  wire,  in  place  of  the 
cylinder.  This  ring,  named  after  its  inventor,  has,  with  more  or 
less  modifications,  become  typical  of  many  machines  of  modern 
construction.  In  the  construction  of  all  older  machines,  steel 
magnets  had  been  used,  and  their  magnetism  not  being  con- 
stant, the  effect  of  the  machine  was  consequently  also  not 
constant.  Furthermore,  they  generated  alternately  negative 
and  positive  currents,  which,  by  means  of  commutators,  had  to 
be  converted  into  currents  of  the  same  direction ;  and  this,  in 
consequence  of  the  vigorous  formation  of  sparks,  caused  the 
rapid  wearing  out  of  the  commutators. 

These  defects  led  to  the  employment  of  continuous  mag- 
netism in  the  iron  cores  of  the  electro-magnets,  the  first 
machine  based  upon  this  principle  being  introduced  in  1866, 
by  Siemens,  which,  in  1867,  was  succeeded  by  Wheatstone's. 

However,  the  first  useful  machine  was  introduced  in  1871, 
by  Zenobe  Gramme,  who  in  its  construction  made  use  of  Paci- 
notti's  ring.  This  machine  was,  in  1872,  succeeded  by  Hefner- 
Alteneck's,  of  Berlin.  In  both  machines  the  poles  of  the  elec- 
tro-magnet exert  an  inducing  action  only  upon  the  outer  wire 
wrappings  of  the  revolving  ring,  the  other  portions  being 
scarcely  utilized,  which  increases  the  resistance  and  causes  a 
useless  production  of  heat.  This  defect  led  to  the  construction 
of  flat- ring  machines,  in  which  the  cylindrical  ring  is  replaced 
by  one  of  a  flat  shape,  and  of  larger  diameter,  thus  permitting 
the  induction  of  both  flat  sides.  Such  a  machine  was,  in  1884, 
built  by  Siemens  &  Halske,  of  Berlin  ;  and  in  the  same  year  by 
S.  Schuckert,  of  Niirenberg.  In  Schuckert's  modern  machines 
nearly  three-quarters  of  all  the  wire  wrappings  are  under  the 
inducing  influence  of  both  of  the  large  pole  shoes  of  the  electro- 
magnets. 

Of  other  constructions  of  dynamo-electrical  machines  maybe 


HISTORICAL    REVIEW    OF   ELECTRO-METALLURGY.  9 

mentioned  Mather's,  Elmore's,  Fein's,  Mohring's,  Krottlinger's, 
and  Lahmeyer's,  the  latter  especially  being  at  the  present  time 
much  employed  in  Germany  for  electro-plating  purposes.  In 
this  country  Weston's  machine  and  the  dynamos  manufactured 
by  the  Hanson  &  Van  Winkle  Co.,  of  Newark,  N.  J.,  the  Zucker 
&  Levett  Chemical  Co.,  of  New  York,  and  others  are  largely 
used  for  electro-plating  purposes. 

For  the  sake  of  completeness,  there  may  be  mentioned  the 
investigators  and  practitioners  who  during  the  last  twenty  years 
have  contributed  much  to  the  improvement  of  the  electro- 
chemical processes  and  the  perfection  of  galvanoplasty.  Be- 
sides those  already  named,  they  are:  Elkington,  Becquerel, 
Heeren,  Roseleur,  Eisner,  von  Leuchtenberg,  Meidinger,  Weil, 
Goode,  Christofle,  Klein,  von  Kress,  Thompson,  Adams,  Giaffe, 
and  others. 


II. 

THEORETICAL     PART, 


CHAPTER  II. 

MAGNETISM  AND  ELECTRICITY. 

i.  MAGNETISM. 

FOR  the  better  understanding  of  the  electrolytic  laws  it  will 
be  necessary  to  commence  with  the  phenomena  presented  by 
magnetism,  and  to  consider  them  more  closely. 

A  particular  species  of  iron  ore  is  remarkable  for  its  property 
of  attracting  small  pieces  of  iron  and  causing  them  to  adhere  to 
its  surface.  This  iron  ore  is  a  combination  of  ferric  oxide  with 
ferrous  oxide  (Fe3O4),  and  is  called  loadstone  or  magnetic  iron 
ore.  Its  properties  were  known  to  the  ancients,  who  called  it 
magnesian  stone  after  Magnesia,  a  city  in  Thessaly,  in  the 
neighborhood  of  which  it  was  found.  If  a  natural  loadstone  be 
rubbed  over  a  bar  of  steel,  its  characteristic  properties  will  be 
communicated  to  the  bar,  which  will  then  be  found  to  attract 
iron  filings  like  the  loadstone  itself.  The  bar  of  steel  thus 
treated  is  said  to  be  magnetized,  or  to  constitute  an  artificial 
magnet.  The  artificial  magnets  thus  produced  may  be  straight 
in  the  shape  of  a  horseshoe,  or  annular ;  but  no  matter  what 
their  form,  the  attractive  force  will  appear  to  be  greatest  at  two 
points  situated  near  the  extremities  of  the  bar,  and  least  of  all 
towards  the  middle.  The  points  of  the  magnet  showing  the 
greatest  attractive  force  are  called  the  magnetic  poles,  whilst  the 
line  between  them,  possessing  little  or  no  attractive  force,  is 
termed  the  neutral  line  or  neutral  zone.  In  a  closed  magnet  the 

(10) 


MAGNETISM    AND   ELECTRICITY.  I  I 

poles  are  situated  on  the  ends  of  one  and  the  same  diameter, 
while  the  neutral  zones  are  located  on  the  ends  of  a  diameter 
standing  perpendicular  to  the  first. 

When  a  magnetized  bar  or  natural  magnet  is  suspended  at 
its  centre  in  any  convenient  manner,  so  as  to  be  free  to  move 
in  a  horizontal  plane,  it  is  always  found  to  assume  a  particular 
direction  with  regard  to  the  earth,  one  end  pointing  nearly 
north  and  the  other  nearly  south.  If  the  bar  be  removed  from 
this  position  it  will  tend  to  reassume  it,  and  after  a  few  oscilla- 
tions, settle  at  rest  as  before.  The  direction  of  the  magnetic 
bar,  i.  e.,  that  of  its  longitudinal  axis,  is  called  the  magnetic  me- 
ridian, while  the  pole  pointing  towards  the  north  is  usually  dis- 
tinguished as  the  north  pole  of  the  bar,  and  that  which  points 
southward  as  the  south  pole. 

A  magnet,  either  natural  or  artificial,  of  symmetrical  form, 
suspended  in  the  presence  of  a  second  magnet,  serves  to  ex- 
hibit certain  phenomena  of  attraction  and  repulsion,  which 
deserve  particular  attention.  When  a  north  pole  is  presented 
to  a  south  pole,  or  a  south  pole  to  a  north,  attraction  ensues 
between  them ;  the  ends  of  the  bar  approach  each  other,  and, 
if  permitted,  adhere  with  considerable  force.  When,  on  the 
other  hand,  a  north  pole  is  brought  near  a  second  north  pole, 
or  a  south  pole  near  another  south  pole,  mutual  repulsion  is 
observed,  and  the  ends  of  the  bar  recede  from  each  other  as  far 
as  possible.  Poles  of  an  opposite  name  attract,  and  poles  of  a 
similar  name  repel  each  other. 

According  to  the  theory  or  hypothesis  proposed  by  Ampere, 
magnetism  is  caused  by  the  presence  of  electric  currents  in  the 
ultimate  particles  of  matter.  This  theory  assumes — 

1.  That    the  ultimate  particles  of    all    magnetizable  bodies 
have  closed  electric  circuits  in  which  electric  currents  are  con- 
tinually flowing. 

2.  That  in  an  unmagnetized  body  these  circuits  neutralize 
one  another,  because  they  have  different  directions. 

3.  That  the  act  of  magnetization  consists  in  such  a  polariza- 
tion of  the  particles   as   will  cause  these   currents   to  flow   in 


12  ELECTRO-DEPOSITION   OF   METALS. 

one  and  the  same  direction,  magnetic  saturation  being  reached 
when  all  the  separate  circuits  are  parallel  to  one  another. 

4.  That  coercive  force  is  due  to  the  resistance  these  circuits 
offer  to  a  change  in  the  direction  of  their  planes. 

Guided  by  these  considerations,  Ampere  produced  a  coil  of 
wire,  called  a  solenoid,  which  is  the  equivalent  of  the  magnetiz- 
ing circuit  assumed  by  his  theory.  It  therefore  follows  that  an 
electric  current  sent  through  a  coil  of  insulated  wire  surround- 
ing a  rod  or  bar  of  soft  iron,  or  other  readily  magnetizable  ma- 
terial, will  make  the  same  a  magnet.  A  magnet  so  produced 
is  called  an  electro-magnet;  the  magnetizing  coil  is  called  a 
helix,  or  solenoid.  The  polarity  of  the  magnet  depends  on  the 
direction  of  the  current,  or  on  the  direction  of  winding  of  the 
helix  or  solenoid.  The  improbability  of  an  electric  current 
continually  flowing  in  a  circuit  without  the  expenditure  of  en- 
ergy, has  led  many  scientific  men  to  reject  Ampere's  theory  of 
magnetism. 

If  an  iron  or  steel  needle  be  suspended  free  in  the  neighbor- 
hood of  a  magnet,  it  assumes  a  determined  direction  according 
to  its  greater  or  smaller  distance  from  the  poles  or  from  the 
neutral  zone ;  however,  before  the  needle  assumes  this  direction 
it  swings  quickly  with  a  shorter  stroke,  or  slowly  with  a  longer 
stroke,  according  to  the  greater  or  smaller  attractive  force  ex- 
erted upon  it.  The  space  within  which  the  magnetic  action  of 
a  magnet  is  exercised  is  called  the  magnetic  field,  and  the  mag- 
netic as  well  as  the  electric  attractions  and  repulsions  are,  ac- 
according  to  Coulomb,  as  the  densities  of  the  fluids  acting  upon 
each  other  and  inversely  as  the  square  of  their  distance. 

2.  ELECTRICITY. 

In  an  ordinary  state  solid  bodies  exhibit  no  attractive  effect 
upon  small  light  particles,  such  as  strips  of  paper,  balls  of  elder- 
pith,  etc ;  but  by  rubbing  many  solid  bodies  with  a  piece  of  dry 
cloth  or  fur  they  acquire  the  property  of  attracting  such  light 
bodies  as  mentioned  above.  The  cause  of  this  phenomenon  is 
called  electricity,  and  the  bodies  which  possess  this  property  of 


MAGNETISM   AND    ELECTRICITY.  13 

becoming  electric  by  friction  are  termed  idio-electrics,  and  those 
which  do  not  appear  to  possess  it,  non- electrics.  Gray,  in  1727, 
found  that  all  non-electric  bodies  conduct  electricity,  and  hence 
are  conductors,  while  those  which  become  electric  by  friction 
are  non-conductors  of  electricity.  Strictly  speaking,  there  are 
no  non-conductors,  because  the  resins,  silk,  glass,  etc.,  conduct 
electricity,  though  only  very  slightly.  It  is  therefore  better  to 
distinguish  good  and  bad  conductors.  To  test  whether  a  body 
belongs  to  the  idio-electrics,  the  so-called  electroscope  is  used, 
which  in  its  simplest  form  consists  of  a  glass  rod  mounted  on  a 
stand,  and  bent  at  the  top  into  a  hook,  from  which  hangs  by  a 
silken  thread  or  hair  a  pith  ball.  If,  on  bringing  the  rubbed 
body  near  the  pith  ball,  the  latter  is  attracted,  the  body  is  elec- 
tric ;  whilst  if  the  ball  is  not  attracted,  the  body  is  either  non- 
electric or  its  electricity  is  too  slight  to  produce  an  attractive 
effect. 

From  the  following  experiments  it  was  found  that  there  exist 
two  kinds  of  electricity:  When  a  rubbed  rod  of  glass  or  shellac 
is  brought  near  the  ball  of  elder-pith  suspended  to  a  silk  thread, 
the  ball  is  attracted,  touches  the  rod,  adheres  for  a  few  moments 
and  is  then  repulsed.  This  repulsion  is  due  to  the  fact  that  the 
ball  by  coming  in  contact  with  the  rod  becomes  itself  electric, 
and  its  electricity  must  first  be  withdrawn  by  touching  with  the 
hand  before  it  can  again  be  attracted  by  the  rod.  By  now 
taking  two  such  balls,  one  of  which  has  been  made  electric  by 
touching  with  a  glass  rod,  which  had  been  rubbed  with  silk, 
and  the  other  by  touching  with  a  shellac  rod  rubbed  with  cloth, 
it  will  be  observed  that  the  ball,  which  is  repulsed  by  the  glass 
rod,  is  attracted  by  the  shellac  rod,  and  vice  versa.  These  two 
kinds  of  electricity  are  called  vitreous  or  positive,  and  resinous 
or  negative  electricity,  and  it  has  been  found  that  electricities  of 
a  similar  name  attract,  and  electricities  of  an  opposite  name  re- 
pel, each  other. 

For  want  of  a  concrete  knowledge  of  the  electric  agent  which 
produces  the  electric  phenomena,  various  theories  or  hypotheses 
have  been  advanced  to  explain  these  phenomena  and  the  action 


14  ELECTRO-DEPOSITION   OF   METALS. 

of  the  electric  forces.  Only  two  of  the  best  known  theories  or 
hypotheses,  shall  here  be  mentioned. 

Double  fluid  hypothesis  of  electricity.  By  this  hypothesis  it 
is  endeavored  to  explain  the  causes  of  electric  phenomena  by 
the  assumption  of  the  existence  of  two  different  electric  fluids. 

The  double  fluid  hypothesis  assumes:  — 

1.  That  the  phenomena  of  electricity  are  due  to  two  tenuous 
and  imponderable  fluids,  the  positive  and  the  negative. 

2.  That  the  particles  of  the  positive  fluid  repel  one  another, 
as  do  also  the  particles  of  the  negative  fluid ;   but  that  the  par- 
ticles of  the  positive  fluid  attract  the  particles   of  the  negative, 
and  vice  versa. 

3.  That  the  two  fluids  are  strongly  attracted  by  matter,  and 
when  present  in  it  produce  electrification. 

4.  That  the  two  fluids  attract  one  another  and  unite,  thus 
masking  the  properties  of  each. 

5.  That  the  act  of  friction  separates  these  fluids,  one  going 
to  the  rubber  and  the  other  to  the  thing  rubbed. 

Single  fluid  hypothesis  of  electricity.  By  this  hypothesis  it  is 
endeavored  to  explain  the  cause  of  electric  phenomena  by  the 
assumption  of  the  existence  of  a  single  electric  fluid. 

The  single  fluid  hypothesis  assumes:  — 

1.  That  the  phenomena  of  electricity  are  due  to  the  presence 
of  a  single,  tenuous,  imponderable  fluid. 

2.  That  the  particles  of  this  fluid  mutually  repel  one  another, 
but  are  attracted  by  all  matter. 

3.  That  every  substance   possesses  a  definite  capacity  for 
holding  the  assumed  electric  fluid,  and  that  when  this  capacity 
is  just  satisfied,  no  effects  of  electrification  are  manifest. 

4.  That  when  the  body  has  less  than  this  quantity  present,  it 
becomes  negatively  excited,  and  when  it  has  more,  positively 
excited. 

5.  That  the  act  of  friction  causes  a  redistribution  of  the  fluid, 
part  of  it  going  to  one  of  the  bodies,  giving  it  a  surplus,  thus 
positively  electrifying  it,  and  leaving  the  other  with  a  deficit, 
thus  negatively  electrifying  it. 


MAGNETISM    AND    ELECTRICITY.  15 

However,  the  epoch-making  investigations  of  Prof.  Herz,  of 
Bonn  (1889),  have  led  to  different  views  regarding  the  nature 
of  electricity.  Herz  has  shown  by  experiments  that  electricity 
is  transmitted  in  space  by  waves  like  heat  and  light,  and  he  has 
determined  the  length  and  velocity  of  electrical  waves.  From 
this  it  has  been  ascertained  that  electricity  is  founded  upon 
motion,  and  that  the  current  appearing  in  a  conductor  has  to 
be  referred  to  vibrations  of  the  molecules  forming  the  conduc- 
tor, relatively  to  vibrations  of  the  ether  enveloping  the  mole- 
cules. By  the  term  ether  is  designated  the  imponderable 
medium  pervading  all  space.  Hence  electricity  is  an  energy, 
just  the  same  as  light  and  heat  are  manifestations  of  energy. 

According  to  Coulomb,  the  electric  attractions  and  repulsions 
are  as  the  densities  of  the  fluids  acting  upon  each  other,  and  in- 
versely as  the  square  of  the  distance. 

However,  a  current  of  electricity  is  created  not  only  by  fric- 
tion, but  also  by  the  contact  of  various  metals.  In  the  same 
manner  as  the  copper  and  iron  in  Galvani's  experiments  with 
the  frog -leg,  other  metals  and  conductors  of  electricity  also  be- 
come electric  by  contact,  the  electric  charges  being,  however, 
stronger  or  weaker,  according  to  the  nature  of  the  metals.  If 
zinc  be  brought  in  contact  with  platinum,  it  becomes  more 
strongly  positively  electric  than  when  in  contact  with  copper ; 
whilst,  however,  copper  in  contact  with  zinc  is  negatively  ex- 
cited, in  contact  with  platinum  it  becomes  positively  electric. 
By  now  arranging  the  metals  in  a  series,  so  that  each  preceding 
metal  becomes  positively  electric  in  contact  with  the  succeed- 
ing one,  a  series  of  electro-motive  force  or  tension  is  obtained,  in 
which  the  metals  or  conductors  of  electricity  sland  as  follows : 

+  Zinc,  cadium,  tin,  iron,  lead,  copper,  nickel, 
Silver,  antimony,  gold,  platinum,  carbon — . 

While  two  metals  of  the  series  of  electro-motive  force  or  tension 
touching  each  other  become  electrically  excited  in  such  a  manner 
that  one  becomes  positively  and  the  other  negatively  electric,  an 
exchange  of  the  opposite  electricities  takes  place  by  introducing 


1 6  ELECTRO-DEPOSITION   OF   METALS. 

a  conducting  fluid  between  the  metals.  Thus,  if  a  plate  of  zinc 
and  a  plate  of  copper  connected  by  a  metallic  wire  are  immersed 
in  a  conducting  fluid,  for  instance,  dilute  sulphuric  acid,  the 
electricity  of  the  positive  zinc  passes  through  the  fluid  to  the 
negative  copper,  and  returns  through  the  wire — the  closing  cir- 
cuit— to  the  zinc.  However,  in  the  same  degree  with  which  the 
electricities  equalize  themselves,  new  quantities  of  them  are 
constantly  formed  on  the  points  of  contact  of  the  metals  with 
the  conducting  fluid ;  and,  hence,  the  flow  of  electricity  is  con- 
tinuous. This  electric  current  generated  by  the  contact  of 
metals  and  fluids  is  called  the  galvanic  current',  or,  since  it  is 
generated  by  the  intervention  of  fluid  conductors,  hydro- electric 
current.  A  combination  of  conductors  which  yields  such  a 
galvanic  current,  is  called  a  galvanic  element  or  galvanic  chain. 

It  would  here  be  the  place  to  discuss  the  various  galvanic 
elements,  but  it  is  thought  better  to  describe  them  in  a  separate 
chapter,  and  first  to  explain  the  laws  and  the  actions  of  the  gal- 
vanic current. 

Electrical  potential. — The  property  of  electricity  correspond- 
ing to  head  or  pressure,  as  applied  in  speaking  of  gas  or  water- 
power,  is  termed  the  electrical  potential.  Two  bodies  have  the 
same  electrical  potential  when,  connected  by  a  metallic  wire, 
they  develop  no  electricity. 

Electro-motive  force. — If,  however,  two  bodies  connected  by  a 
metallic  wire  possess  unequal  electrical  potentials,  a  movement 
of  the  electricity  takes  place,  and  the  force  which  produces  this 
movement  or  current  is  called  the  electro- motive  force  or  ten- 
sion. It,  therefore,  corresponds  to  the  difference  of  the  poten- 
tials ;  and  the  magnitude  of  this  difference  of  the  potentials  is 
the  measure  for  the  electro-motive  force. 

Resistance. — All  conductors  offer  a  certain  amount  of  resist- 
ance to  the  forward  movement  of  the  electric  current.  By  con- 
necting, for  instance,  two  bodies  charged  with  electricity  and 
possessing  a  difference  of  potentials,  by  a  metallic  conductor,  a 
certain  time  is  required  for  the  compensation  of  the  difference 
of  potentials,  or,  in  other  words,  before  the  electrical  equilibrium 


MAGNETISM   AND    ELECTRICITY.  I/ 

is  established.  By  now  keeping  the  difference  of  potentials 
constant,  the  quantity  of  electricity  which  passes  through  the 
closing  conductor — the  closing  circuit — depends  on  the  resist- 
ance which  the  latter  offers  to  the  passage  of  the  current. 

The  resistance  of  a  conductor  is  proportional  to  its  length  and 
inversely  to  its  cross-section  and  its  conducting  capacity ;  i.  e.,  the 
longer  the  conducting  circuit  the  greater  the  resistance,  and  the 
greater  its  cross-sections  the  smaller  the  resistance.  Wires  of 
small  diameter  will,  therefore,  offer  greater  resistance  to  the 
current  than  those  with  larger  diameter,  and  wires  with  good 
conducting  capacity  will  produce  less  resistance  than  those  with 
poor  conducting  capacity.  According  to  Lazere  Weiler,  the 
conductivity  of  metals  is  as  follows:  — 


Name  of  Metal. 

Mean 
Conductivity.- 

Alloys,  etc. 

Mean 
Conductivity. 

Si 

7C  O 

Cu     "12         " 

Si 

75-° 

Gold  

80  6 

p 

•7 

C  C   I 

y 
Cu    "  10        " 

Pb, 

100 

Cu        10        " 

Al. 

126 

16.7 

Cu         10         " 

As, 

Q.I 

.  1 

16  d. 

Cu         20        " 

Sn 

8  A 

Tin 

Zn 

211 

Lead  

8*8 

^u           OD 

86  6 

Nickel  

A^' 

16  i 

Antimony  >  

42 

Sn          12        " 

Na 

4.6  Q 

Quantity  of  current.  Ohm' s  law. — The  quantity  of  electricity 
or,  in  other  words,  the  current  strength,  which  an  element  fur- 
nishes at  a  determined  extreme  point,  depends  on  the  strength 
of  the  electro-motive  force  which  impels  the  current,  as  well  as 
on  the  resistance  which  the  conductor  offers  to  the  current.  In 
the  preceding  it  has  been  seen  that  the  electro-motive  force 
corresponds  to  the  difference  of  the  potentials  of  two  conductors 
connected  by  a  metallic  wire ;  the  greater  this  difference  is,  the 
greater  the  energy  with  which  the  compensation  of  the  elec- 
tricities takes  place.  It  has  also  been  explained  that  the  re- 


18  ELECTRO-DEPOSITION   OF    METALS. 

sistance  increases  in  proportion  to  the  length,  and  decreases 
with  the  increase  in  the  cross-sectfon  of  the  conductor.  Upon 
these  relations  Ohm's  law  is  based,  and  in  its  completeness  it 
may  be  summed  up  as  follows  :  The  quantity  of  electricity  or  the 
strength  (intensity}  of  current  is  directly  proportional  to  the  sum 
of  the  electro-motive  forces  of  the  exciting  elements,  and  is  in- 
versely proportional  to  the  sum  of  the  resistances  of  its  closing 
circuit;  however,  the  resistance  of  each  part  of  the  closing  circuit 
is  proportional  to  its  length  and  inversely  proportional  to  its  cross- 
section.  Now,  if  5  indicates  the  strength  of  current,  E  the  sum 
of  the  electro-motive  forces,  and  L  the  total  resistance,  then  the 
strength  of  current  5  is  — 

S-jj-, 

The  total  resistance  L  is,  however,  composed  of  two  different 
resistances,  namely,  of  the  so-called  essential  or  internal  resist- 
ance, which  expresses  the  resistance  of  the  substances  in  the 
elements  themselves,  and  of  the  non-essential  or  external  resist- 
ance of  the  closing  circuit.  If,  therefore,  the  internal  resistance 
—  R  and  the  external  resistance  =  r,  the  total  resistance  will 
be  L  =  R  +  r,  and  the  formula  given  above  is  changed  to 


R  \-r 

Let  us  now  examine  the  useful  applications  which  result  from 
Ohm's  law,  to  the  coupling  of  the  elements,  they  being  of  great 
importance  to  the  practical  electro-plater.  According  to  the 
above  formula,  which  expresses  the  total  performance  of  a  bat- 
tery, the  strength  of  current  of  a  single  element  is,  if  s  indicates 
its  current  strength,  e  the  electro-motive  force,  R  the  essential 
or  internal  resistance,  and  r  the  resistance  in  the  closing  circuit, 


R+r 

By  now  uniting  several  such  elements,  let  us  say  n  elements, 
to  a  column,  the  electro-motive  force  of  the  latter  has  become 
n  -f  e  =  ney  and  the  internal  resistance  nr;  with  the  same 
closing  circuit  as  that  of  the  single  element,  r  will  not  increase, 
hence  the  strength  of  these  n  elements  must  be  written — 


MAGNETISM    AND    ELECTRICITY.  1 9 


~  n  R  +  r 

It  is  now  clear  that  when  a  determined  closing  circuit  of  the 
resistance  r  is  given  that  the  strength  of  current  cannot -be  in- 
definitely augmented  by  increasing  the  number  of  n  elements ; 
because,  though  the  electro-motive  force,  by  the  augmentation 
of  n  elements,  increases  by  so  many  n,  the  internal  resistance  R 
also  grows,  so  that  finally  the  value  r,  which  remains  constant, 
disappears,  contrary  to  the  resistance  R,  which  increases  n 
times.  Hence,  the  strength  of  current  constantly  approaches 
more  the  limit  of  value — 


On  the  other  hand,  the  effect  can  neither  be  increased  by 
enlarging  the  area  of  the  pair  of  plates  nor  by  decreasing  the 
resistance  of  the  fluid  in  a  given  number  of  elements.  Because 
when  r,  the  external  resistance,  is  sufficiently  large  so  that  the 
internal  resistance,  n  R,  may  be  neglected,  the  intensity  always 

& 
approaches  more  the  value  — . 

Hence,  it  follows  that  the  augmentation  of  the  area  of  the  ex- 
citing pair  of  plates  produces  an  increase  in  the  current-strength 
only  when  the  external  resistance  in  the  closing  circuit  is  small 
in  proportion  to  the  internal  resistance  of  the  battery. 

If  we  now  apply  the  results  of  the  above  explanations  to 
practice,  we  find  that  the  elements  may  be  coupled  in  various 
ways  according  to  requirement. 

i.  If,  for  instance,  four  Bunsen  elements  (carbon-zinc)  are 
coupled  one  after  another  in  such  a  manner  that  the  zinc  of  one 
element  is  connected  with  the  carbon  of  the  next,  and  so  on 
(Fig.  2),  the  current  passes  four  times  in  succession  through 
an  equally  large  layer  of  fluid,  in  consequence  of  which  the  in- 
ternal resistance,  4  R,  is  four  times  greater  than  that  of  a  single 
element,  while  the  resistance  of  the  closing  circuit,  r,  remains 
the  same.  Hence,  while  the  current-strength  is  thereby  not  in- 
creased, the  electro-motive  force  is,  and  for  this  reason  this 


20 


ELECTRO-DEPOSITION    OF   METALS. 


mode  of  coupling  is  called  the  union  or  coupling  of  the  elements 
for  electro-motive  force  or  tension. 


FIG.  2. 


2.  By  connecting  four  elements  alongside  of  each  other,  i.  e., 
all  the  zinc  plates  and  all  the  carbon  plates  one  with  another 

FIG.  3. 


FIG.  4. 


(Fig.  3),  the  current  simultaneously  passes  through  the  same 
layer  of  fluid  in  four  places ;  the  internal  resistance  of  the  bat- 
tery is  therefore  the  same  as  that  of  a  single  element,  and  since 
the  area  of  the  plates  is  four  times  larger  than  that  of  a  single 

element,  the  quantity  of  current  is  aug- 
mented by  this  mode  of  coupling. 
This  is  called  coupling  for  quantity  of 
current. 

3.  Two  elements  may,  however,  be 
connected  for  electro-motive  force  or 
tension,  and  several  such  groups 
coupled  alongside  of  each  other  as 
shown  in  Fig.  4,  whereby,  according 
to  what  has  above  been  said,  the 
electro-motive  force  as  well  as  the  cur- 
augmented. 


This 


rent    strength    is 
mode  of  connection  is  called  mixed  coupling. 

According  to  the  resistance  of  the  bath,  as  well  as  of  the  ex- 
terior closing  circuit,  and  the  surfaces  to  be  plated,  the  electro- 


MAGNETISM   AND    ELECTRICITY.  21 

plater  may  couple  his  elements  in  either  way,  and  in  speaking 
later  on  of  the  elements  the  various  modes  of  coupling  will 
be  further  discussed.  We  will  here  only  mention  the  proposi- 
tion deduced  from  Ohm's  law  that  a  number  of  galvanic  elements 
yield  the  maximum  of  intensity  of  current  when  they  are  so 
arranged  that  the  internal  resistance  of  the  battery  is  equal  to  the 
resistance  in  the  closing  circuit.  Hence,  when  operating  with 
baths  of  good  conductivity  and  slight  resistance,  for  instance, 
acid  copper  baths,  silver  cyanide  baths,  etc.,  with  a  slight  dis- 
tance between  the  anodes  and  the  objects,  and  with  a  large 
anode-surface,  it  will  be  advantageous  to  couple  the  elements 
alongside  of  each  other  for  quantity ;  however,  for  baths  with" 
greater  resistance  and  with  a  greater  distance  of  the  anodes  from 
the  objects,  and  with  a  smaller  anode  surface,  it  is  best  to 
couple  the  elements  one  after  the  other  for  electro-motive  force  or 
tension. 

The  effects  of  the  electric  current  are  thermal,  physiological, 
electro-magnetic,  inductive,  and  chemical ;  however,  for  our 
purposes,  only  the  last  three  need  be  discussed. 

Electro-magnetism. 

If  a  wire  conveying  the  electric  current  be  brought  near  a 
magnetic  needle,  the  latter  will  immediately  be  deflected  from 
its  direction,  no  matter  whether  the  wire  conveying  the  current 
be  placed  alongside,  above,  or  beneath  the  magnetic  needle. 
The  direction  which  the  needle  will  assume  when  placed  in  any 
particular  position  to  the  conducting  wire,  may  be  determined 
by  the  following  rule:  Let  the  current  be  supposed  to  pass 
through  a  watch  from  the  face  to  the  back :  the  motion  of  the 
north  pole  will  be  in  the  direction  of  the  hands.  Or,  let  the  ob- 
server imagine  himself  swimming  in  the  direction  of  the  current 
with  his  face  towards  the  needle :  the  north  pole  of  the  needle  will 
then  be  deflected  towards  his  left  hand. 

When  the  needle  is  subjected  to  the  action  of  two  currents  in 
opposite  directions,  the  one  above  and  the  other  below,  they 
will  obviously  concur  in  their  effects.  The  same  thing  happens 


22  ELECTRO-DEPOSITION    OF   METALS. 

when  the  wire  carrying  the  current  is  bent  upon  itself  and  the 
needle  placed  between  the  two  portions ;  and  since  every  time 
the  bending  is  repeated  a  fresh  portion  of  the  current  is  made 
to  act  in  the  same  manner  upon  the  needle,  it  is  easy  to  see  how 
a  current,  too  feeble  to  produce  any  effect  when  a  simple  straight 
wire  is  employed,  may  be  made  by  this  contrivance  to  exhibit 
a  powerful  action  on  the  magnet.  It  is  on  this  principle  that 
instruments  called  galvanoscopes,  galvanometers,  or  mtdtipliers 
are  constructed.  They  serve  not  only  to  indicate  the  existence 
of  electrical  currents,  but  also  to  show  by  the  effects  upon  the 
needle  the  direction  in  which  they  are  moving.  The  delicacy  of 
the  instrument  has  been  increased  by  Nobili  through  the  use  of 
a  very  long  coil  of  wire,  and  by  the  addition  of  a  second  needle. 
This  instrument  is  known  as  the  astatic  galvanometer.  The  two 
needles  are  of  equal  size  and  magnetized  as  nearly  as  possible 
to  the  same  extent ;  they  are  then  immovably  fixed  together 
parallel  and  with  their  poles  opposed,  and  hung  by  a  long  fibre 
of  untwisted  silk,  with  the  lower  needle  in  the  coil  and  the  upper 
one  above  it.  The  advantage  thus  gained  is  twofold :  the  sys- 
tem is  astatic,  unaffected,  or  nearly  so,  by  the  magnetism  of  the 
earth ;  and  the  needles  being  both  acted  upon  in  the  same 
manner  by  the  current,  are  urged  with  much  greater  force  than 
one  alone  would  be,  all  the  actions  of  every  part  of  the  coil 
being  strictly  concurrent.  A  divided  circle  is  placed  below  the 
upper  needle,  by  which  the  angular  motion  can  be  measured, 
and  the  whole  is  inclosed  in  glass,  to  shield  the  needles  from  the 
agitation  of  the  air. 

The  deflection  of  the  magnetic  needle  by  the  electric  current 
has  led  to  the  construction  of  instruments  which  allow  of  the 
intensity  of  the  current  being  measured  by  the  magnitude  of 
the  deflection.  Such  instruments  are,  for  instance,  the  tangent 
galvanometer,  the  sine  galvanometer,  etc.,  but  they  are  almost 
exclusively  used  for  scientific  measurements,  while  for  the  de- 
termination of  the  intensity  of  current  for  electro -plating  pur- 
poses other  instruments  are  employed,  which  will  be  described 
later  on.  However,  the  electric  current  exerts  not  only  a  re- 


MAGNETISM   AND    ELECTRICITY.  23 

fleeting  action  on  magnetic  needles,  but  is  also  capable  of  pro- 
ducing a  magnetizing  effect  on  iron  and  steel.  If  a  bar  of  iron 
be  surrounded  by  a  coil  of  wire,  covered  with  silk  or  cotton  for 
the  purpose  of  insulation,  it  becomes  magnetic  so  long  as  the 
current  is  conducted  through  the  coil.  Such  iron  bars  con- 
verted into  temporary  magnets  by  the  action  of  the  current  are 
called  electro-magnets,  and  they  will  be  more  highly  magnetic 
the  greater  the  number  of  turns  of  the  coil,  and  the  more  intense 
is  the  current  passing  through  the  turns. 

However,  not  only  the  iron  bar,  around  which  the  current 
circulates,  becomes  magnetic,  but  also  a  conducting  wire 
through  which  passes  a  strong  current.  By  suspending  a  cir- 
cular conducting  wire  so  that  it  is  free  to  move  around  its  ver- 
tical axis,  its  direction  is  affected  by  the  magnetism  of  the 
earth,  and  it  will  take  up  a  position  so  that  its  plane  stands  at 
a  right  angle  to  the  plane  of  the  magnetic  meridian ;  by  now 
conducting  the  current  through  a  wire  having  the  form  of  a 
long  helix,  a  so-called  solenoid,  the  wire  will,  in  a  like  manner, 
place  itself  with  the  turns  of  the  helix  at  right  angles  to  the 
plane  of  the  magnetic  meridian,  or,  in  other  words,  the  axis  of 
the  solenoid  will  lie  in  the  magnetic  meridian. 

In  the  same  manner  as  an  electrified  conducting  wire  acts 
upon  a  magnet,  two  electrified  wires  exert  an  attracting  and  re- 
pelling influence  on  each  other,  the  general  law  of  the  action 
being  that  electric  currents  moving  in  parallel  lines  attract  one 
another  if  they  move  in  the  same  direction,  and  repel  one  another 
if  they  move  in  opposite  directions. 

Induction. 

By  induction  is  understood  the  production  of  an  electric  cur- 
rent in  a  closed  circuit  which  is  in  the  immediate  neighborhood 
of  a  current-carrying  wire. 

Suppose  we  have  two  insulated  copper  wire  spirals,  A  and  B 
(Fig.  5),  B  being  of  smaller  diameter  and  inserted  in  A.  When 
the  two  ends  of  B  are  connected  with  the  poles  of  a  battery  a 
current  is  formed  in  A  the  moment  the  current  of  B  is  closed. 


24 


ELECTRO-DEPOSITION    OF   METALS. 


This  current  is  recorded  by  the  deflection  of  the  magnetic 
needle  of  a  multiplier,  M,  which  is  connected  with  the  ends  of 
A,  the  deflection  of  the  needle  showing  that  the  current  pro- 
duced in  A  by  the  current  in  B  moves  in  an  opposite  direction. 
The  current  in  A,  however,  is  not  lasting,  because,  after  a  few 
oscillations,  the  magnetic  needle  of  the  multiplier  returns  to  its 
previous  position  and  remains  there,  no  matter  how  long  the 
current  may  pass  through  B.  If,  however,  the  current  in  B  be 
interrupted,  the  magnetic  needle  swings  to  the  opposite  direc- 
tion, thus  indicating  the  formation  of  a  current  in  A,  which 
passes  through  it  in  the  same  direction  as  the  interrupted 
current  in  B. 

FIG.  5. 


The  current  causing  this  phenomenon  is  called  the  primary 
or  inductive  current,  and  that  produced  by  it  in  the  closed  cir- 
cuit the  secondary  or  induced  current.  From  what  has  been 
above  said,  it  is  clear  that  an  electric  current  at  the  moment  of 
its  formation  induces  in  a  neighboring  closed  circuit  a  current  of 
opposite  direction,  but  when  interrupted,  a  current  of  the  same 
direction. 

In  the  same  manner   as  closing  and   opening  the   inductive 


MAGNETISM   AND    ELECTRICITY.  25 

current,  its  sudden  augmentation  also  effects  the  induction  of  a 
current  of  opposite  direction  in  a  neighboring  wire,  while  its 
sudden  weakening  induces  a  current  of  the  same  direction ;  the 
same  effect  being  also  produced  by  bringing  the  inductive  wire 
closer  to,  or  removing  it  further  from,  the  neighboring  wire. 
The  induced  currents  being  alternately  formed  by  opening  and 
closing  the  circuit,  and  they  showing  different  directions,  the 
term  alternating  currents  has  been  applied  to  them. 

If  the  turns  of  the  spirals  are  very  close  together,  each  turn 
induces  the  other,  the  so-called  extra  currents  being  thereby 
formed. 

The  induced  currents  follow  Ohm's  law  the  same  as  the  in- 
ductive current.  A  long  inducing  wire  with  a  small  cross-sec- 
tion offers  greater  resistance  than  a  short  wire  with  a  larger 
cross-section,  and  consequently  in  the  first  case  the  current  will 
possess  slighter  intensity  and  higher  tenison,  and  in  the  other 
greater  intensity  and  less  tenison. 

In  the  same  manner  as  an  electrified  wire  induces  a  current 
in  a  neighboring  wire,  a  magnet  or  electro-magnet  also  produces 
induced  currents  in  a  coil  of  wire  surrounding  it.  These  cur- 
rents act  in  the  same  manner  as  those  produced  by  other 
means,  and  by  taking  into  consideration  Ohm's  law,  currents  of 
great  and  slight  intensity  can  be  produced  at  will,  as  will  be 
seen  in  speaking  of  the  dynamo-electric  machines,  the  construc- 
tion of  which  is  based  upon  the  principle  of  induction. 

Chemical  actions  of  the  electrical  current — Electrolysis. 

An  electric  current  on  being  conducted  through  a  fluid  effects 
the  reduction  of  its  constituents.  By  cutting,  for  instance,  the 
conductor  of  an  electric  current,  and  introducing  the  two  wire 
ends  thereby  formed  into  water  acidulated  with  dilute  sulphuric 
acid,  the  water,  provided  the  current  is  strong  enough,  is  de- 
composed into  its  constituents,  hydrogen  and  oxygen,  the 
former  separating  in  the  form  of  gas  on  the  negative  pole  and 
the  latter  on  the  positive.  If  such  a  decomposition  does  not 
take  place,  the  fluid  does  not  conduct  the  current.  Pure  water 


26  ELECTRO- DEPOSITION  OF  METALS. 

by  itself  is  a  bad  conductor,  and  to  make  its  decomposition 
possible  it  has  to  be  made  conductive  by  acidulation  with  dilute 
sulphuric  acid.  When  a  chemical  composition  is  decomposed 
by  the  current,  the  constituent  forming  the  basis  of  the  combi- 
nation separates  on  the  negative  pole,  and  that  constituting  the 
acid  on  the  positive ;  hence  metals  and  hydrogen  are  liberated 
on  the  negative,  and  acids  and  oxygen  on  the  positive  pole.  To 
Faraday  is  due  the  discovery  of  the  chemical  actions  of  the 
current  and  the  exposition  of  the  laws  governing  the  separation 
of  the  constituents.  He  adopted  the  term  electrolysis  for  the 
electrical  separation  of  chemical  combinations,  and  electrolyte 
ior  the  fluids  subjected  to  electrical  decomposition.  To  the 
poles  or  plates  leading  the  current  into  and  out  of  the  electro- 
lyte he  applied  the  term  electrodes,  the  positive  pole  being  the 
anode,  and  the  negative  pole  the  cathode.  The  elements  of  the 
electrolyzed  liquid,  which  are  liberated  by  the  action  of  the 
current,  are  termed  ions,  those  set  free  on  the  anode  or  positive 
electrode  being  termed  anions,  and  those  at  the  cathode  or 
negative  anode  cations.  Thus,  when  acidulated  water  is  electro- 
lyzed, two  ions  are  evolved,  namely,  oxygen  and  hydrogen,  the 
former  at  the  positive  and  the  latter  at  the  negative  electrode. 

It  is  absolutely  necessary  for  the  electrolyte  to  be  in  a  fluid 
state,  though  it  does  not  matter  whether  the  fluid  state  is  pro- 
duced by  solution  or  fusion. 

We  know  no  more  of  the  actual  cause  of  the  chemical  action 
of  electricity  than  of  its  nature  and  origin.  According  to 
Clausius'  theory,  matter  is  composed  of  minute  particles  called 
molecules,  which,  though  mechanically  indivisible,  are  chem- 
ically divisible.  The  constituent  parts  of  the  molecules  which 
are  no  further  chemically  divisible  are  called  atoms.  Clausius 
supposes  that  the  molecules  are  in  constant  motion ;  that  in 
solid  bodies  they  move  around  determined  positions  of  equi- 
librium, while  in  fluids  even  apparently  tranquil  they  move  from 
one  place  to  another,  constantly  revolving  and  pushing  against 
one  another  without  being  subjected  to  a  return  to  their  original 
positions.  In  pushing  against  one  another  the  molecules  are 


MAGNETISM   AND    ELECTRICITY.  27 

decomposed  into  the  atoms  of  which  they  are  composed ;  those 
atoms,  however,  which  have  become  electro-negative  under  the 
influence  of  the  current  endeavor  to  reach  the  anode,  while  those 
which  have  become  electro-positive  move  towards  the  cathode. 
But  in  doing  this  they  meet  atoms  of  opposite  polarity,  with 
which  they  reunite  to  a  molecule  until  they  are  again  liberated 
by  this  molecule  pushing  against  another,  when  they  move 
further  towards  the  anode.  Arriving  at  the  electrodes,  they 
find  no  more  atoms  of  opposite  polarity  with  which  they  might 
unite  to  a  molecule ;  both  atoms,  therefore,  remain  free  on  the 
electrodes,  while  the  electrolyte  between  the  two  electrodes 
suffers  no  perceptible  change.  The  atoms  are,  therefore,  to  be 
considered  as  ions.  However,  in  order  that  the  ions  may  be 
attracted  by  the  electrodes,  a  current  of  determined  electro- 
motive force  is  required ;  as  otherwise,  though  the  electrolyte 
may  conduct  the  current,  the  atoms  attract  one  another  more 
vigorously  than  they  are  attracted  by  the  electrode,  and  again 
form  molecules.  To  this  mutual  attraction  of  the  atoms  of  oppo- 
site polarity  is  due  the  resistance  of  the  electrolyte  to  the  trans- 
mission of  the  current,  and  also  the  formation  of  a  current  of  an 
opposite  direction  to  that  of  the  primary  current,  which  is  called 
the  counter  or  polarizing  current.  This  counter  current,  which 
is  so  effectually  utilized  with  accumulators  (secondary  batteries), 
is  the  worst  enemy  of  the  electro-plater,  and  to  overcome  it 
very  strong  currents  have  frequently  to  be  used,  as  will  be 
shown,  for  instance,  in  nickeling  sheet  zinc. 

Faraday  is  also  the  discoverer  of  the  following  electrolytic 
laws : 

First  law.  The  quantity  of  substance  separated  within  a  de- 
termined time  by  the  current  is  directly  proportional  to  the  strength 
of  the  current.  By  conducting  the  current  through  a  volt- 
meter (Fig.  6),  i.  e.t  a  closed  decomposing  cell  provided  with 
two  platinum  electrodes,  which  are  in  contact  with  the  poles  of 
the  element,  and  dip  into  acidulated  water,  oxygen  evolves  on 
the  positive  electrode  and  hydrogen  on  the  negative.  The  gas 
mixture  (oxyhydrogen  gas)  is  conducted  through  a  bent  tube 


28 


ELECTRO-DEPOSITION    OF   METALS. 


FIG.  6. 


inserted  air-tight    in  the    stopper    of   the  cell,  into  graduated 
."..;  tubes,  in   such    a   manner  that  the 

gas  enters  the  tubes  under  water. 
The  escaping  mixture  of  gas  rises  in 
the  form  of  bubbles  into  the  upper 
part  of  the  tube,  and  the  volume  of 
gas  there  collected  in  a  determined 
time  can  be  readily  read  off. 

Now,  if  a  current  of  determined 
strength  has  produced  a  determined 
quantity  of  oxyhydrogen  gas  in  the 
voltmeter,  a. current  twice  as  strong 
will,  according  to  Faraday's  law, 
produce  in  the  same  time  double 
the  volume  of  gas,  from  which 
further  results  the  fact  that  for  the 
decomposition  of  a  determined 
quantity  of  any  body,  a  constant 
quantity  of  current  is  always  re- 
quired, to  which  the  term  electrical  eqivalent  might  be  applied. 
Second  law.  If  the  same  current  acts  upon  a  series  of  differ- 
ent solutions,  the  weights  of  the  elements  separated  at  the  same 
time  in  each  solution  are  proportional  to  their  chemical  equivalents. 
If,  for  instance,  the  same  current  be  conducted  through  three 
decomposing  cells,  one  of  which  contains  water,  the  second  a 
solution  of  blue  vitriol,  and  the  third  a  solution  of  nitrate  of 
silver,  for  each  gramme  of  hydrogen  developed  in  the  first  cell, 
31.75  grammes  of  copper  will  be  separated  in  the  second  cell, 
and  1 08  grammes  of  silver  in  the  third  cell,  because  their 
chemical  equivalents  are  as  I  :  31.75  :  108. 

Third  law.  In  an  element,  the  chemical  decomposition — the 
dissolution  of  zinc — is  proportional  to  the  strength  of  current ;  or, 
in  other  words,  as  many  equivalents  of  zinc  are  dissolved  in  the 
element  as  equivalents  of  another  metal  are  separated  in  an  in- 
serted electrolyte.  Every  electro-plater  observes  that  the  zinc 
cylinders  of  the  elements  are  dissolved ;  and  it  is  just  this  solu- 


MAGNETISM   AND    ELECTRICITY.  2Q 

tion  which  maintains  the  development  of  the  electric  current. 
As  is  well  known,  zinc  is  strongly  attacked  and  dissolved  by 
dilute  sulphuric  acid;  therefore  a  dissolution  of  zinc  takes  place 
before  the  galvanic  apparatus  is  closed.  This  dissolution  of 
zinc,  independent  of  the  production  of  current,  is  termed  local 
action,  and  to  decrease  it  the  zinc  is  amalgamated  by  first  wash- 
ing it  with  strong  soda  to  remove  grease.  Then  it  is  dipped 
into  a  vessel  of  water  containing  TV  of  sulphuric  acid.  As 
soon  as  strong  action  takes  place  it  is  transferred  to  a  suitable 
dish,  mercury  poured  over  it,  and  finally  is  rubbed  till  a  bright 
silver-like  film  forms  ;  then  it  is  set  up  on  edge  to  drain,  and 
before  use  any  globules  set  free  are  rubbed  off.  If  local  action 
has  thus  been  prevented,  only  as  much  zinc  will  dissolve, 
according  to  this  law,  as  is  chemically  equivalent  to  the  metal 
separated  in  the  decomposing  cell.  If,  however,  local  action  is 
present,  the  consumption  of  zinc  is  increased  by  the  quantity 
corresponding  to  solution  by  local  action. 

Electro-chemical  equivalents. — This  term  is  applied  to  the 
weights  of  the  various  electrolytes  which  are  decomposed  in 
the  unit  of  time  by  the  electric  unit.  The  electro-chemical 
equivalents  are  proportional  to  their  chemical  equivalents.  The 
electro-chemical  equivalent  of  a  body  is  found  by  multiplying 
its  chemical  equivalent  by  the  electro-chemical  equivalent  of 
hydrogen=o.ooo  1 022 . 

When  an  electric  current  passes  through  a  conductor,  the 
latter  becomes  more  or  less  heated.  According  to  Joule's  ex- 
periments, it  was  found  that  the  development  of  heat  in  the  con- 
ductor is  proportional  to  its  resistance;  and  further,  that  it  is  pro- 
portional to  the  square  oj  the  strength  of  current. 

Hence  the  development  of  heat  will  be  the  greater  the  smaller 
the  cross-section  of  the  conductor  and  its  conducting  capacity 
are,  and  the  larger  the  quantity  of  current  which  passes  through 
it.  For  practical  purposes,  the  conclusion  derived  from  this  is 
the  necessity  of  choosing  conducting  wire  of  good  conducting 
capacity  and  of  sufficiently  large  diameter  to  prevent  the  devel- 
opment of  heat,  which  in  this  case  means  loss  of  current. 


30  ELECTRO-DEPOSITION    OF    METALS. 

Consumption  of  power  in  electrolysis. — Without  a  desire  fur- 
ther to  enter  into  the  details  of  the  electro-chemical  theory,  it 
may  for  the  sake  of  completeness,  be  mentioned  that  the  force 
required  for  the  decomposition  of  an  electrolytic  solution  is  at  least 
equal  to  that  which,  when  converted  into  heat,  corresponds  to  the 
heat  developed  by  the  separated  bodies  in  their  reunion  into  their 
original  combination. 

Electric  units. — The  electro-motive  force  required  for  the  de- 
composition being  frequently  given,  as  well  as  the  intensity 
which  the  current  must  possess  in  order  properly  to  coat  a  de- 
termined surface  of  article  with  the  electrolytically  separated 
metal,  the  electric  units  serving  for  electric  measures  will  be 
briefly  given : 

To  measure  the  physical  phenomena  of  the  current  it  is  nec- 
essary to  refer  to  mass,  length,  and  duration  of  time,  and  the 
units  adopted  by  the  International  Congress  of  1881  are  as  fol- 
lows : — 

1.  Unit  of  length,  I  centimetre. 

2.  Unit  of  time,  I  second. 

3.  Unit  of  mass,  the  mass  of  one  gramme. 

The  term  fundamental  or  C.  G.  S.  (centimetre-gramme-sec- 
ond) units  has  been  applied  to  this  system. 

Force  or  power  (F) — Dyne. — Force  which  acting  upon  I 
gramme  for  a  second  generates  a  velocity  of  I  centimetre  per 
second. 

Work — Erg. — Amount  of  work  done  by  I  dyne  working 
through  i  centimetre  of  distance. 

Quantity. — The  quantity  conveyed  by  unit  current  in  i 
second. 

Potential  or  electro-motive  force. — The  difference  of  the  electric 
condition  between  two  conductors  or  two  points  of  a  conductor, 
when  the  transference  of  electricity  from  one  to  the  other  is 
proceeding  at  the  rate  of  i  erg  of  work  per  unit  of  electricity 
transferred. 

Resistance. — A  resistance  such  that  with  unit  of  difference  of 
potential  between  the  ends  of  conductor,  I  unit  of  current  is 
conveyed  along  it. 


MAGNETISM   AND    ELECTRICITY.  31 

Of  the  so-called  practical  units,  which  were  retained  by  the 
Congresses  and  Conferences  of  1881  and  1884,  there  are  five: 
the  ohm,  volt,  ampere,  farad,  and  coulomb. 

The  ohm  is  the  practical  unit  of  resistance.  It  is  equal  to  the 
resistance  of  a  column  of  mercury  I  metre  long  and  I  square 
millimetre  in  cross-sectional  area  at  o°  C.,  and  approximately 
"equal  to  the  resistance  of  48.5  metres  of  pure  copper  wire,  I 
millimetre  in  diameter,  at  O°C.  The  ohm  is  equal  to  io9  C.  G. 
S.  units. 

The  ampere  is  the  practical  unit  of  the  current-strength  (in- 
tensity) ;  it  is  equal  to  T^  of  the  theoretical  C.  G.  S.  unit.  For 
practical  purposes  the  quantity  of  silver  precipitated  in  one 
second  is  taken  as  the  representative  value  of  an  ampere, 
0.0011188  gramme  of  silver  corresponding,  according  to  Kohl- 
rausch,  to  one  ampere. 

The  volt  is  the  practical  unit  of  the  electro-motive  force,  and 
is  equal  to  io8  C.  G.  S.  units.  It  is  approximately  equal  to  the 
electro-motive  force  of  a  single  Daniell's  cell. 

'The  farad  is  the  practical  unit  of  capacity  equal  to  io9  C.  G. 
S.  units ;  the  coulomb  is  the  unit  of  quantity,  i.  e.,  the  volume 
of  current  equal  to  that  of  I  ampere  passing  through  a  circuit 
for  one  second  of  time. 

A  current  of  I  ampere  at  the  pressure  of  I  volt  is  termed  a 
watt;  it  is  a  most  useful  unit  for  comparing  different  currents, 
and  is  really  the  product  of  volume  into  pressure. 

The  English  horse-power  (H.  P.)  is  taken  at  550  foot-pounds 
per  second,  and  is  thus  equivalent  to  raising  550  pounds 
through  one  foot,  or  one  pound  through  550  feet,  in  a  second. 
(The  French  H.  P.  is  542.48  foot-pounds  per  second.) 


Ill 

SOURCES    OK    CURRENT. 


CHAPTER  III. 

GALVANIC   ELEMENTS — THERMO-PILES — MAGNETO-   AND 
DYNAMO-ELECTRIC   MACHINES. 

THE  sources  of  current  used  for  electro-deposition  of  metals 
are  the  galvanic  elements,  thermo-piles,  magneto-electric  machines, 
and  dynamo- electric  machines. 

A.   GALVANIC  ELEMENTS. 

It  is  not  proposed  to  enter  into  a  detailed  description  of  all 
the  forms  of  galvanic  elements,  because  the  number  of  such 
constructions  is  very  large,  while  the  number  of  those  which 
have  been  successfully  and'permanently  introduced  for  practical 
work  is  comparatively  small. 

The  original  form  of  the  galvanic  elements,  the  voltaic  pile, 
consisting  of  zinc  and  copper  plates  separated  from  one  another 
by  moist  pieces  of  cloth,  has  been  already  mentioned  on  p.  2, 
as  well  as  its  disadvantages,  which  led  to  the  construction  of  the 
so-called  trough  battery.  The  separate  elements  of  this  battery 
are  square  plates  of  copper  and  zinc,  soldered  together  and 
parallel,  fixed  into  water-tight  grooves  in  the  sides  of  a  wooden 
trough  so  as  tofconstitute  water-tight  partitions,  which  are  filled 
with  acidulated  |water.  The  layer  of  water  serves  here  as  a 
substitute  for  the  moist  pieces  of  cloth  in  the  voltaic  pile. 

In  other  constructions  the  fluid  is  in  different  vessels,  each 
vessel  containing  a  zinc  and  a  copper  plate  which  do  not  touch 


GALVANIC    ELEMENTS.  33 

one  another  in  the  same  vessel,  the  copper  plate  of  the  one 
vessel  being  connected  with  the  zinc  plate  of  the  next,  and  so  on. 

In  all  elements  with  one  fluid  as  an  excitant,  the  current  is 
quite  strong  at  first,  but  quickly  decreases  for  the  following  rea- 
sons :  First,  during  the  interruption  of  the  current,  a  change 
takes  place  in  the  fluid  by  the  local  action  in  the  element,  and 
then  with  a  closed  circuit  the  zinc  with  the  impurities  it  con- 
tains forms  small  voltaic  piles,  the  element  consequently  also 
performing  a  certain  chemical  work  during  the  interruption  of 
the  current.  As  mentioned  on  p.  29,  the  local  action  can  be 
reduced  to  a  minimum  by  amalgamating  the  zinc.  Such 
amalgamation  is  also  a  protection  against  the  above-mentioned 
chemical  work  of  the  element,  the  bubbles  of  hydrogen  adher- 
ing so  firmly  to  the  amalgamated  homogeneous  surface  as  to 
form  a  layer  of  gas  around  the  zinc  surface,  which  prevents  its 
contact  with  the  fluid. 

Amalgamation  may  be  effected  in  various  ways.  The  zinc  is 
either  scoured  with  coarse  sand  moistened  with  dilute  sulphuric 
or  hydrochloric  acid,  or  pickled  in  a  vessel  containing  either  of 
the  dilute  acids.  The  mercury  may  be  either  mixed  with 
moist  sand  and  a  few  drops  of  dilute  sulphuric  acid,  and  the 
zinc  be  amalgamated  by  applying  the  mixture  by  means  of  a 
wisp  of  straw  or  a  piece  of  cloth ;  or  the  mercury  may  be  ap- 
plied by  itself  by  means  of  a  steel  wire  brush,  the  brush  being 
dipped  in  the  mercury,  and  what  adheres  quickly  divided  upon 
the  zinc  by  brushing  until  the  entire  surface  acquires  a  mirror- 
like  appearance.  The  most  convenient  mode  of  amalgamation 
is  to  dip  the  zinc  in  a  suitable  solution  of  a  mercury  salt  and 
rub  with  a  woollen  rag.  A  suitable  solution  is  prepared  by  dis- 
solving 10  parts  by  weight  of  mercurous  nitrate  in  100  parts  of 
warm  water,  to  which  pure  nitric  acid  is  added  until  the  milky 
turbidity  disappears.  Another  solution,  which  is  also  highly 
recommended,  is  obtained  by  dissolving  10  parts  by  weight  of 
mercuric  chloride  (corrosive  sublimate)  in  12  parts  of  hydro- 
chloric acid  and  100  of  water.  In  order  to  preserve  as  much 
as  possible  the  coating  of  mercury  upon  the  zinc,  sulphuric 
3 


34  ELECTRO-DEPOSITION    OF    METALS. 

acid  saturated  with  neutral  mercuric  sulphate  is  used  for  the  ele- 
ments ;  for  which  purpose  frequently  shake  the  concentrated  sul- 
phuric acid  (before  diluting  with  water)  with  the  mercury  salt. 

Bouant  recommends  instead  of  the  addition  of  mercuric  sul- 
phate, to  compound  the  dilute  sulphuric  acid  with  2  per  cent, 
of  a  solution  obtained  as  follows:  Boil  a  solution  of  3}^  ozs.  of 
nitrate  of  mercury  in  I  quart  of  water,  with  an  excess  of  a  mix- 
ture of  equal  parts  of  mercuric  sulphate  and  mercuric  chloride, 
and,  after  cooling,  filter  and  use  the  clear  solution. 

The  third  reason  for  the  decrease  of  the  current-strength  in 
elements  with  one  fluid  is  polarization.  By  polarization  is  un- 
derstood the  appearance  in  the  element  of  a  second  current 
which,  being  opposite  to  that  produced  by  the  element,  weak- 
ens the  action  of  the  latter.  The  cause  of  galvanic  polarization 
is  found  in  the  fact  that  the  negative  pole-plate  becomes  coated 
with  a  layer  of  hydrogen,  whereby  according  to  Clausius's  the- 
ory (p.  26)  the  attraction  of  the  anodes  for  the  ions  is  essenti- 
ally weakened,  while,  according  to  another  theory,  the  electro- 
negative plate,  by  contact  with  the  layer  of  gas,  becomes  elec- 
tro-positive towards  the  other,  which  is  coated  with  bubbles  of 
oxygen. 

Polarization  can  only  be  entirely  avoided  in  elements  the  neg- 
ative pole-plate  of  which  dips  into  a  fluid  which  oxidizes  the 
hydrogen  to  water,  as  is  the  case  in  the  so-called  constant  ele- 
ments with  two  fluids,  as  will  be  seen  later  on. 

Proceeding  from  the  conviction  that  rough  surfaces  allow  the 
bubbles  of  hydrogen  to  pass  off  much  more  freely  than  smooth 
surfaces,  Smee  constructed  the  element  named  after  him.  It 
consists  of  a  zinc  plate  and  a  platinized  silver  plate  dipping  into 
dilute  acid.  It  may  be  formed  of  two  zinc  plates  mounted  with 
the  platinized  silver  between  them  in  a  wooden  frame,  which 
being  a  very  feeble  conductor  may  carry  away  a  minute  fraction 
of  the  current,  but  serves  to  hold  the  metals  in  position,  so  that 
quite  a  thin  sheet  of  silver  may  be  employed  without  fear  of  its 
bending  out  of  shape  and  making  a  short  circuit.  The  platin- 
izing is  effected  by  hanging  the  silver  plates  in  a  vessel  filled 


GALVANIC    ELEMENTS. 


35 


with  acidulated  water,  adding  some  chloride  of  platinum,  and 
placing  the  vessel  in  a  porous  clay  cell  filled  with  acidulated 
water  and  containing  a  piece  of  zinc,  the  latter  being  connected 
with  the  silver  plates  by  copper  wire.  The  platinizing  obtained 
in  this  manner  is  a  black  powder  which  roughens  the  surfaces, 
in  consequence  of  which  the  bubbles  of  hydrogen  become  read- 
ily detached  and  the  polarization  is  less  than  with  silver  plates 
not  platinized.  The  use  of  electrolytically  prepared  copper 
plates,  which  are  first  strongly  silvered  and  then  platinized,  is 
still  more  advantageous  on  account  of  their  greater  roughness. 
To  increase  the  constancy  of  the  element,  it  is  advisable  to  add 
some  chloride  of  platinum  to  the  dilute  acid  of  the  element. 
The  electro-motive  force  of  the  Smee  element  is  about  0.48 
volt. 

As  previously  mentioned,  polarization  can  be  entirely  avoided 
only  by  allowing  the  electro-negative  pole  plate  to  dip  in  a  fluid 
which,  by  combustion,  reduces  the  hydrogen  evolved  to  water, 
or,  in  other  words,  which  immediately  oxidizes  the  hydrogen  to 
water.  From  this  conviction  originated  the  so-called  constant 
elements  with  two  fluids,  the  first  of  these 
elements  being,  in  1829,  constructed  by 
Becquerel,  which,  in  1836,  was  succeeded 
by  the  far  more  effective  one  of  Daniell. 

As  most  generally  used,  Daniell's  element 
(Fig.  7)  consists  of  a  glass  vessel,  a  copper 
cylinder,  a  porous  clay  cell,  and  a  rod  of 
zinc  suspended  in  the  latter.  The  glass 
vessel  is  filled  with  concentrated  solution 
and  a  small  piece  of  blue  vitriol,  and  the 
porous  clay  cell  with  dilute  sulphuric  acid. 
The  oxygen  evolved  on  the  electro-positive  zinc  oxidizes  the 
latter,  sulphate  of  zinc  being  formed,  while  the  hydrogen  sep- 
arating on  the  electro-negative  copper  reduces  from  the  blue 
vitriol  solution  a  quantity  of  copper  equivalent  to  it,  which  sep- 
arates upon  the  electro-negative  plate.  However,  after  a  com- 
paratively short  time  of  working,  the  dilute  sulphuric  acid  is 


FIG.  7. 


ELECTRO-DEPOSITION   OF   METALS. 


FIG.  8. 


consumed  for  the  formation  of  sulphate  of  zinc,  the  electro- 
motive force  becoming  very  weak.  The  necessity  of  frequently 
renewing  the  dilute  sulphuric  acid  is  an  inconvenience  whfch 
the  Daniell  elements  show  more  than  any  others.  Furthermore, 
by  the  action  of  osmose,  blue  vitriol  solution  gets  into  the  por- 
ous cell,  where  it  is  decomposed  by  coming  in  contact  with  the 
zinc,  the  copper  being  separated  upon  the  latter,  whereby  the 
effect  is  destroyed  or  at  least  very  much  weakened.  The  electro- 
motive force  of  the  Daniell  element  is  about  I  volt. 

The  Meidinger  element  may  be  considered  a  modified  Daniell 
element.  Like  the  Callaud  element,  it  has  no  porous  division, 
the  mixture  of  the  two  fluids  being  prevented  by  their  different 
specific  gravities.  The  shape  of  the  Meidinger  element,  as 
most  generally  used,  is  shown  in  Fig.  8. 

Upon  the  bottom  of  a  glass  vessel,  A, 
provided  at  b  with  a  shoulder,  stands  a 
small  glass  cylinder,  K,  which  contains 
the  electro-negative  copper  cylinder  D  ; 
from  the  latter  a  conducting  wire  leads 
to  the  exterior.  Upon  the  shoulder,  at  b, 
rests  the  zinc  cylinder  Z,  which  is  also 
provided  with  a  conducting  wire  leading 
to  the  exterior.  The  balloon  C  closes 
the  vessel  by  being  placed  upon  it.  The 
balloon  is  filled  with  pieces  of  blue 
vitriol  and  Epsom  salt  solution ;  the  en- 
tire element  is  also  filled  with  Epsom  salt 
solution  (i  part  Epsom  salt  to  5  water). 
In  the  balloon  C  concentrated  solution  of 

blue  vitriol  is  formed  which  flows  into  the  glass  cylinder  K.  If 
the  circuit  is  not  closed,  the  concentrated  copper  solution  re- 
mains quietly  standing  in  K,  its  greater  specific  gravity  pre- 
venting it  from  rising  higher  and  reaching  the  zinc.  If,  how- 
ever, the  circuit  be  closed,  zinc  is  dissolved,  while  metallic 
copper  is  separated  from  the  blue  vitriol  solution,  and  concen- 
trated solution  flows  from  the  balloon  C  to  the  same  extent  as 


GALVANIC    ELEMENTS.  37 

the  blue  vitriol  solution  in  D  becomes  dilute  by  the  separation 
of  copper.  Hence  the  action  of  the  element  remains  constant 
for  quite  a  long  time,  and  of  all  the  modified  forms  of  Daniell's 
element  consumes  the  least  blue  vitriol  for  a  determined 
quantity  of  current.  However,  in  consequence  of  its  great  in- 
ternal resistance  (9.90  ohms)  its  current-strength  is  small.  The 
electro-motive  force  of  the  Meidinger  element  is  0.95  volt. 

Grove,  in  1839,  substituted  platinum  for  copper ;  the  platinum 
dips  in  concentrated  nitric  acid,  while  the  zinc  cylinder  stands  in 
dilute  sulphuric  acid.  The  hydrogen  liberated  on  the  platinum 
is  oxidized  to  water  by  the  nitric  acid,  hyponitrous  acid 
escaping  in  the  form  of  gas.  The  electro- motive  force  of  the 
Grove  element  is  at  first  double  that  of  the  Daniell  element,  but 
it  soon  abates  on  account  of  the  dilution  of  the  nitric  acid  by 
water.  To  prevent  this  weakening,  concentrated  sulphuric 
acid,  which  absorbs  the  water  formed  by  the  oxidation  of  the 
hydrogen,  may  be  added  to  the  nitric  aeid.  Though  the  resist- 
ance of  the  Grove  element  is  small  (0.70  to  0.75  ohm),  and  its 
electro-motive  force  1.70  to  I.QO  volts,  according  to  the  con- 
centration of  the  solutions,  it  is  but  seldom  used  on  account  of 
its  costliness. 

Bunsen,  in  1841,  replaced  the  expensive  platinum  by  prisms 
cut  from  gas-carbon,  which  is  still  less  electro-negative  than 
platinum,  and  very  hard  and  solid,  so  that  it  perfectly  resists 
the  action  of  the  nitric  acid.  In  place  of  the  gas- carbon  an 
artificial  carbon  may  be  prepared  by  kneading  a  mixture  of 
pulverized  coal  and  coke  with  sugar  solution  or  syrup,  bringing 
the  mass  under  pressure  into  suitable  iron  moulds  and  glowing 
it  with  the  exclusion  of  air.  After  cooling,  the  carbon  is  again 
saturated  with  sugar  solution  (others  use  tar,  or  a  mixture  of 
tar  and  glycerine)  and  again  glowed  with  the  exclusion  of  air, 
these  operations  being,  if  necessary,  repeated  once  more,  es- 
pecially when  great  demands  are  made  on  the  electro-motive 
force  and  solidity  of  the  artificial  carbons. 

Figs.  9,  10,  and  1 1  show  the  three  forms  of  Bunsen's  elements 
most  generally  used. 


ELECTRO-DEPOSITION    OF    METALS. 


Fig.  9,  which  is  the  most  convenient  and  practical  form,  con- 
sists of  an  outer  vessel  of  glass.  In  this  is  placed  a  cylinder  of 
zinc  in  which  stands  a  porous  clay  cell,  and  in  the  latter  the 
prism  of  gas-carbon.  This  substance  is  the  graphite  of  the  gas 
retorts.  It  is  not  coke.  It  is  easily  procurable  in  lump  at  a 
small  price,  but  costs  much  more  when  cut  into  plates,  as 
its  working,  when  the  material  is  good,  is  exceedingly  dim- 
cult.  It  is  generally  cut  with  a  thin,  strip  of  iron  and  watered 
silver-sand.  Blocks  for  Bunsen  cells  cost  less  because  they  are 
more,  easily  produced.  Rods  for  Bunsen  cells  should  be  a  few 
inches  longer  than  the  pots  to  protect  the  top  contact  from  the 
acid.  A  good  carbon  is  of  a  clear  gray  appearance,  has  a  finely 
granulated  surface,  and  is  very  hard.  A  band  of  copper  is  sol- 
dered or  secured  by  means  of  a  binding-screw  to  the  zinc  cyl- 
inder while  the  prism  of  gas-carbon  carries  the  binding-screw 
(armature),  as  seen  in  Fig.  9,  in  the  upper  part  of  which  acop- 


FIG.  9. 


FIG.  10. 


FIG.  ii. 


per  sheet  or  wire  is  fixed  for  the  transmission  of  the  current. 
The  outer  vessel  is  filled  with  dilute  sulphuric  acid  ( I  part  by 
weight  of  sulphuric  acid  of  66°  Be. — free  from  arsenic — and  1 5 
parts  by  weight  of  water),  and  the  porous  cell  with  concentrated 
nitric  acid  of  at  least  36°  Be.,  or  still  better  40°  Be.,  care  being 
had  that  both  fluids  have  the  same  level. 

In  Fig.  10  the  cylinder  of  artificial  carbon  is  in  the  glass  ves- 


GALVANIC    ELEMENTS. 

sel,  while  the  zinc,  which,  in  order  to  increase  its  surface,. has  a 
star-like  cross-section,  is  placed  in  the  porous  clay  cell.  In  this 
case  the  outer  vessel  is  filled  with  concentrated  nitric  acid,  and 
the  clay  cell  with  dilute  sulphuric  acid. 

The  form  of  the  Bunsen  element  shown  in  Fig.  9  is  more 
advantageous,  because  its  effective  zinc  surface  can  be  kept 
larger.  Fig.  1 1  shows  a  plate  element  such  as  is  chiefly  used 
for  bichromate  batteries. 

FIG.  12. 


Fig.  12  shows  an  improved  Bunsen  cell  of  great  power  for 
nickel  and  electro-plating,  electro-motors,  etc.  It  has  an  electric- 
motive  force  of  1.8  volts.  When  the  absence  of  power  prevents 
the  use  of  a  dynamo,  a  battery  of  these  cells  is  very  suitable  for 
nickel-plating.  It  is  an  easy  battery  to  set  up  and  keep  in 
working  order.  The  batteries  are  set  up  by  well  amalgamating, 
inside  and  outside  the  zinc,  and  placing  it  in  the  jar.  Inside 
the  zinc  place  the  porous  cup,  and  within  the  porous  cup  the 
carbon,  and  then  pour  nitric  acid  in  the  porous  cup.  In  the 
outer  jar  pour  a  mixture  of  I  part  sulphuric  acid  to  12  of  water 
(previously  mixed  and  allowed  to  cool).  This  acid  mixture 
should  cover  the  zinc  or  be  on  a  level  with  the  liquid  in  the 
porous  cup.  When  the  liquid  in  the  outer  jar  becomes  milky, 


40  ELECTRO-DEPOSITION   OF   METALS. 

withdraw  it  with  a  syringe  or  siphon,  and  refill,  adding  occa- 
sionally small  quantities  of  nitric  acid  to  the  porous  cup,  and 
keeping  the  zinc  thoroughly  amalgamated  by  one  of  the  methods 
given  on  page  33.  A  very  good  plan  of  amalgamating  zinc  is 
as  follows :  Dip  in  lye  to  remove  grease,  rinse,  then  dip  in  the 
dilute  acid  in  the  glass  jar,  and  then  brush  over  with  about  2 
ozs.  of  mercury  contained  in  a  little  flannel  bag. 

Electro poion  may  be  substituted  for  the  nitric  acid  in  the  por- 
ous cup.  This  battery  liquid  consists  of  I  Ib.  of  bichromate  of 
potash  dissolved  in  10  Ibs.  of  water,  to  which  2^/2  Ibs.  of  com- 
mercial sulphuric  acid  have  been  gradually  added. 

The  Bunsen  elements  are  much  used  for  electro-deposition, 
since  they  possess  a  high  electro- motive  force  (1.88  volts)  and, 
on  account  of  slight  resistance  (0.25  ohm),  develop  consider- 
able current- strength.  Like  the  Grove  elements,  they  have  the 
inconvenience  of  evolving  vapors  of  hyponitrous  acid,  which 
are  not  only  injurious  to  health,  but  also  attack  the  metallic 
articles  in  the  workshop.  Wherever  possible  they  should  be 
placed  in  a  box  at  such  a  height  that  they  may  be  readily 
manipulated.  This  box  should  have  means  of  ventilation  in 
such  a  way  that  the  air  coming  in  at  the  lower  part  will  escape 
at  the  top  through  a  flue,  and  carry  away  with  it  the  acid  fumes 
disengaged.  It  is  still  better  to  keep  the  elements  in  a  room 
separate  from  that  where  the  baths  and  metals  are  to  be  ope- 
rated upon.  Furthermore,  as  the  nitric  acid  becomes  diluted  by 
the  oxidation  of  the  hydrogen,  and  the  sulphuric  acid  is  con- 
sumed in  the  formation  of  sulphate  of  zinc,  the  acids  have  to  be 
frequently  renewed. 

To  avoid  the  acid  vapors,  as  well  as  to  render  the  elements 
more  constant,  A.  Dupre  has  proposed  the  use  of  a  30  per  cent, 
solution  of  bisulphate  of  potash  in  water  in  place  of  the  dilute 
sulphuric  acid,  and  a  mixture  of  water  600  parts,  concentrated 
sulphuric  acid  400,  sodium  nitrate  500,  and  bichromate  of 
potash  6c,  in  place  of  the  nitric  acid. 

The  following  method  can  be  recommended :  The  outer 
vessel  which  contains  the  zinc  cylinder  is  filled  with  a  mode- 


GALVANIC    ELEMENTS.  4! 

rately  concentrated  (about  30  per  cent.)  solution  of  bisulphate 
of  potash  or  soda,  and  the  clay  cell  with  solution  of  chromic 
acid — I  part  chromic  acid  to  5  parts  water.  As  soon  as  the 
electro-motive  force  of  the  element  abates,  it  is  strengthened  by 
the  addition  of  a  few  spoonfuls  of  pulverized  chromic  acid  to 
the  chromic  acid  solution.  It  is  better  to  use  the  chromic  acid 
in  the  form  of  powder,  which  is  especially  prepared  for  this 
purpose,  than  a  chromic  acid  solution  produced  by  mixing  solu- 
tion of  bichromate  of  potash  with  sulphuric  acid,  the  tendency 
of  such  a  solution  to  form  crystals  exerting  a  disturbing  effect. 

The  chromic  acid  solution  loses  effect  in  a  comparatively 
short  time,  the  electro-motive  force  decreasing  in  a  few  hours, 
and  chromic  acid  must  be  added,  or  the  cell  refilled. 

Another  soluble  chromium  combination  which  depolarizes 
with  rapidity  and  maintains  the  constancy  of  the  elements  for 
a  much  longer  time,  is  obtained  by  treating  pulverized  chrome- 
ironstone  with  concentrated  sulphuric  acid  and  careful  dilution 
with  water.  With  a  single  filling  of  this  solution  the  battery 
could  be  kept  working  for  six  days  from  morning  to  evening 
without  refilling  being  required.  During  the  night  the  battery 
remained  filled,  but  inactive.  The  electro-motive  force  of  an 
element  filled  with  the  chromium  solution  is  to  be  sure  some- 
what less  than  when  nitric  or  chromic  acid  is  used,  it  amount- 
ing to  1.5  volts,  but  on  account  of  the  great  constancy  and 
consequent  cheapness  of  the  filling,  the  fact  that  an  additional 
element  has  to  be  added  for  a  bath  requiring  a  greater  tension 
than  3  volts  for  decomposition  need  not  be  taken  into  con- 
sideration. 

In  using  nitric  acid  it  is  also  advantageous  to  pour  a  0.39  to 
0.78  inch  thick  layer  of  oil  upon  the  acid,  to  decrease  the 
vapors. 

The  binding  screws  which  effect  the  metallic  contacts  must 
of  course  be  frequently  inspected  and  cleaned,  which  is  best 
done  by  means  of  a  file  or  emery  paper.  It  is  advisable  to 
place  a  piece  of  sheet  platinum  between  the  binding  surface  of 
the  carbon  armature  and  the  carbon  in  order  to  prevent  the 


-42  ELECTRO-DEPOSITION   OF   METALS. 

acid  rising  through  the  capillarity  of  the  carbon  from  acting 
directly  upon  the  armature  (generally  brass  or  copper).  To 
prevent  the  acid  from  rising,  the  upper  portions  of  the  carbons 
may  be  impregnated  with  paraffine.  For  this  purpose  the  car- 
bons are  placed  f  to  I  inch  deep  in  melted  paraffine  and  allowed 
to  remain  10  minutes.  On  the  sides  where  the  armature  comes 
in  contact  with  the  carbon,  an  excess  of  paraffine  is  removed  by 
scraping  with  a  knife-blade  or  rasp. 

Manipulation  of  Bunsen  elements. — Before  using  the  elements 
the  zinc  cylinders  should  be  very  carefully  amalgamated  accord- 
ing to  one  of  the  methods  given  on  p.  33.  The  nitric  acid  need 
not  be  pure,  the  crude  commercial  acid  sufficing,  but  it  should 
be  as  concentrated  as  possible  and  show  at  least  36°  Be.  For 
the  prisms  it  is  best  to  take  carbon  produced  in  gas-houses 
using  coal  without  the  addition  of  brown  coal,  the  electro- 
motive force  of  the  latter  being  less.  If  artificial  carbon  is  em- 
ployed, it  should  be  examined  as  to  its  suitability,  the  non- 
success  of  the  plating  process  being  frequently  attributed  to  the 
composition  of  the  bath,  when  in  fact  it  is  due  to  the  defective 
carbons  of  the  elements.  In  order  to  avoid  an  unnecessary 
consumption  of  zinc  and  acid,  the  elements  are  taken  apart 
when  not  in  use,  for  instance,  over  night.  Detach  the  brass 
armature  of  the  carbon  prism  and  lay  it  in  water  to  which  some 
chalk  has  been  added ;  lift  the  carbon  from  the  clay  cylinder 
and  place  it  in  a  porcelain  dish  or  earthenware  pot ;  empty  the 
nitric  acid  of  the  clay  cell  into  a  bottle  provided  with  a  glass 
stopper;  place  the  clay  cell  in  a  vessel  of  water,  and  finally 
take  the  zinc  cylinder  from  the  dilute  sulphuric  acid  and  place 
it  upon  two  sticks  of  wood  laid  across  the  glass  vessel  to  drain 
off.  In  putting  the  elements  together  the  reverse  order  is  fol- 
lowed, the  zinc  being  first  placed  in  the  glass  vessel  and  then 
the  carbon  in  the  porous  clay  cell.  The  latter  is  then  filled 
about  three-quarters  full  with  used  nitric  acid,  and  fresh  acid  is 
added  until  the  fluid  in  the  clay  vessel  stands  at  a  level  with 
that  in  the  outer  vessel.  The  cleansed  brass  armature  is  then 
screwed  upon  the  carbon  prism.  Finally,  add  to  the  dilute 


GALVANIC    ELEMENTS. 


43 


FIG.  13. 


sulphuric  acid  in  the  outer  vessel  a  small  quantity  of  concen- 
trated sulphuric  acid  saturated  with  mercury  salt. 

It  is  advisable  to  have  at  least  a  duplicate  set  of  porous  clay 
cells,  and  in  putting  the  elements  together  to  use  only  cells 
which  have  been  thoroughly  soaked  in  water.  The  reason  for 
this  is  as  follows :  The  nitric  acid  fills  the  pores  of  the  cell,  and, 
finally  reaching  the  zinc  of  the  outer  vessel,  causes  strong  local 
action  and  a  correspondingly  rapid  destruction  of  the  zinc.  It 
is,  therefore,  best  to  change  the  clay  cells  every  day,  allowing 
those  which  have  been  in  use  to  lie  in  water  the  next  day  with 
frequent  renewal  of  the  water.  For  the  same  reason  the  nitric 
acid  in  the  clay  cell  should  not  be  at  a  higher  level  than  the 
sulphuric  acid,  in  the  outer  .vessel. 

When  the  Bunsen  elements  are'in  steady  use  from  morning 
till  night,  the  acids  will  have  to  be 
entirely  renewed  every  third  or 
iourth  day.  The  solution  of  sul- 
phate of  zinc  in  the  outer  vessel  is 
thrown  away,  while  the  acid  of  the 
clay  cells  may  be  mixed  with  an 
equal  volume  of  concentrated  sul- 
phuric acid,  and  this  mixture  can 
be  used  as  a  preliminary  pickle  for 
brass  and  other  copper  alloys. 

Foote  s  pinnacle  gravity  battery. 
Gravity  batteries  are  especially 
suited  for  continuous  work  at  a  low 
rate,  the  operating  cost  being  as 
low  as,  if  not  lower  than,  any  other 
type  of  battery.  Four  of  these  cells 
in  series  will  charge  a  small  storage 
battery.  The  type  of  gravity  shown  in  Fig.  13  is  one  of  the 
best  in  the  market. 

The  battery  is  set  up  by  placing  the  copper  cross  and  zinc 
in  position.  Pour  clean  water  into  the  jar  until  within  two 
inches  of  the  top,  then  drop  in  blue  vitriol  (sulphate  of  copper) 


44 


ELECTRO- DEPOSITION    OF   METALS. 


in  small  lumps.  The  battery  may  be  made  immediately  avail- 
able by  adding  4  ozs.  of  pulverized  sulphate  of  zinc.  When  the 
hydrometer  reads  less  than  15°  Be.,  there  is  not  enough  zinc 
sulphate  in  solution ;  when  over  30°  Be.,  there  is  too  much. 

Oppermann  s  element  is  in  the  main  a  Bunsen  element,  but  is 
distinguished  from  the  latter  by  nitric  acid  containing  molybdic 
acid  being  used  as  depolarizing  fluid  instead  of  pure  nitric  acid. 
It  is  also  provided  with  a  hollow  porcelain  body  upon  the  clay 

FIG.  14. 


cell.  This  porcelain  body  is  filled  with  a  solution  of  potassium 
permanganate,  whereby  the  escaping  vapors  are  mostly  ren- 
dered innocuous.  Furthermore,  the  element  when  at  rest  con- 
sumes no  material.  To  avoid  the  inconvenience  of  emptying 
the  elements,  Oppermann  has  provided  his  battery  jars,  close 
above  the  bottoms,  with  two  tubulures  opposite  to  one  another. 
This  arrangement  allows  of  all  the  jars  of  a  battery  being  con- 
nected with  one  another,  as  shown  in  Fig.  14.  The  first  jar  of 
the  battery  is  connected  by  means  of  a  rubber  tube  of  suitable 


GALVANIC    ELEMENTS.  45 

length  with  a  large  tubulated  supply-jar,  while  one  of  the 
tubulures  of  the  last  jar  is  provided  with  a  massive  rubber 
stopper.  The  supply-jar  contains  the  exciting  fluid  for  the  ex- 
terior cells. 

The  clay  cell  of  the  Oppermann  element  is  closed  by  a 
hollow  porcelain  lid.  The  latter  contains  a  fluid  capable  of 
absorbing  or  decomposing  the  vapors  evolved  by  the  decompo- 
sition of  the  depolarizing  fluid  containing  nitric  acid.  In  the 
centre  of  the  porcelain  lid  is  a  square  hole  in  which  the  carbon 
prism  is  secured.  The  fluid  in  the  lid  consists  of  a  solution  of 
potassium  permanganate  acidulated  with  a  small  quantity  of 
sulphuric  acid.  The  solution  is  prepared  as  follows :  Dissolve 
I  part  by  weight  of  pure  potassium  permanganate  in  20  parts 
by  weight  of  distilled  water,  and  add  to  the  solution  about  I 
part  by  weight  of  dilute  sulphuric  acid.  The  vapors  of  hypo- 
nitrous  acid  are  absorbed  with  avidity  by  this  solution,  and 
oxidized  partly  to  nitrous  acid  and  partly  to  nitric  acid.  Both 
of  these  acids  combine  with  the  potassium  or  the  manganous 
oxide,  and  the  potassium  permanganate  solution,  which  exhibits 
at  first  a  deep  violet  color,  is  finally  completely  decolorized. 
When  this  is  the  case,  which  will  be  in  about  3  or  4  hours,  the 
solution  has  to  be  renewed.  This  is  done  in  the  simplest 
manner  by  introducing  about  5  ccm.  of  the  solution  into  the  lid 
by  means  of  a  pipette,  whereby  the  solution  consumed  is  forced 
from  the  lid,  passes  into  the  clay  cell  and  enriches  the  depolar- 
izing fluid  by  the  addition  of  fresh  nitric  or  nitrous  acid. 

The  arrangement  of  the  elements  and  their  combination  to  a 
battery  is  effected  as  follows :  The  battery  jars  are  placed  as 
indicated  in  the  illustration  and  connected  with  one  another  by 
means  of  rubber  stoppers,  glass  tubes  bent  at  a  right  angle  and 
short  pieces  of  rubber  hose.  It  is  advisable  first  to  dip  the 
rubber  stoppers  in  water,  then  to  press  them  firmly  into  the 
tubulures  and  finally  to  insert  the  glass  tubes  also  previously 
moistened  with  water.  For  the  sake  of  security  the  rubber 
stoppers  are  fastened  to  the  tubulus  with  cord  or  wire.  One 
tubulus  each  of  the  two  end  jars,  however,  remains  free.  The 


46  ELECTRO-DEPOSITION    OF   METALS. 

free  tubulus  of  the  last  jar  is  tightly  closed  with  a  massive 
rubber  stopper,  while  that  of  the  first  jar  is  provided  with  a  per- 
forated stopper  and  a  glass  tube,  and  is  connected  with  the 
supply-jar  by  means  of  a  rubber  hose  of  suitable  length. 

In  the  battery-jars  thus  connected  the  zinc  cylinders  are  first 
placed,  and  next  in  the  latter  the  clay  cells,  and  finally  in  the 
clay  cells  the  carbon  prisms.  The  clay  cells  are  then  filled 
with  the  depolarizing  fluid.  The  porcelain  lids  are  next  placed 
upon  the  carbon  prisms  and  the  brass  binding-screws  secured 
to  the  prisms.  The  size  of  the  porcelain  lids  must  be  such  that 
they  reach  into  the  clay  cells  and  are  about  even  with  the  upper 
edge  of  the  latter.  The  holes  on  the  upper  side  of  the  porce- 
lain lids  remain  open.  For  filling  the  lids  with  potassium  per- 
manganate solution  a  pipette  is  used.  At  5  ccm.  the  pipette  is 
provided  with  a  mark  and  it  is  filled  up  to  that  point  by  dipping 
it  in  the  fluid  or  by  suction.  The  upper  opening  is  then  closed 
with  the  index  finger  of  the  right  hand  and  the  point  of  the 
pipette  introduced  into  the  hole  of  the  lid.  By  now  removing 
the  finger  the  contents  of  the  pipette  run  into  the  lid. 

For  filling  the  outer  cells  it  is  best  to  use  a  concentrated  solu- 
tion of  common  salt,  which  is  prepared  by  dissolving  35  parts 
by  weight  of  common  salt  in  100  parts  by  weight  of  water. 
Should  the  solution  be  very  turbid,  it  has  to  be  filtered.  This 
is  also  necessary  in  case  the  solution,  while  in  use,  deposits  a 
muddy  sediment.  In  place  of  common  salt  solution,  a  concen- 
trated sal  ammoniac  solution  may  be  used.  It  is  prepared  by 
dissolving  25  parts  by  weight  of  sal  ammoniac  in  75  parts 
by  weight  of  water.  Dilute  sulphuric  acid  (i  part  by  weight  of 
pure  sulphuric  acid  in  30  parts  by  weight  of  water),  with  an 
addition  of  a  small  quantity  of  neutral  sulphate  of  mercury,  is 
also  suitable  as  an  exciting  fluid.  Common  salt  solution,  how- 
ever, deserves  preference ;  and  its  action  can  be  strengthened 
by  the  addition  of  a  very  small  quantity  of  dilute  sulphuric  acid. 
The  exciting  fluid  is  brought  into  the  supply-jar.  The  ordinary 
element  is  7.87  inches  in  height  and,  when  this  size  is  used, 
the  supply-jar  must  have  a  capacity  of  at  least  as  many  quarts 


GALVANIC    ELEMENTS.  47 

as  there  are  elements  in  the  battery.  To  fill  the  jars  the 
supply-jar  is  placed  at  a  higher  level  and  the  cock  opened. 
The  solution  then  runs  into  all  the  battery-jars  connected  with 
one  another.  After  connecting  the  copper  band  of  the  zinc 
cylinder  with  the  binding-screw  of  the  carbon  of  the  next  ele- 
ment, the  battery  is  ready  for  use.  To  connect  the  end  poles 
of  the  battery  with  the  respective  apparatus,  quite  stout  copper 
wire  thoroughly  insulated  should  be  used.  The  wire  should  be 
at  0.079  inch  in  diameter,  and  be  as  short  as  possible. 

When  work  with  the  battery  is  to  be  interrupted,  the  supply- 
jar  is  placed  at  a  lower  level  and  the  cock  opened.  The  ex- 
citing fluid  then  escapes  from  the  outer  cells  of  the  elements 
and  the  development  of  current  ceases.  While  the  battery  is 
not  in  use,  a  small  portion  of  the  depolarizing  fluid  oozes 
through  the  clay  cells  and  collects  upon  the  bottom  of  the  bat- 
tery-jars. This  fluid  must  be  removed  before  the  battery  is 
again  put  in  operation.  For  this  purpose  the  glass  tubes  bent 
at  a  right  angle  inserted  in  the  tubulures  of  the  jars  are  turned 
so  that  one  leg  points  upwards.  The  rubber  hoses  are  then 
withdrawn,  the  bent  glass  tubes  turned  downward  and  the  jars 
emptied  by  tilting  them.  For  filling  the  clay  cells  with  fresh 
depolarizing  fluid,  a  glass  funnel  with  glass  cock  and  long 
discharge  tube  is  used,  whereby  it  is,  however,  necessary  to 
slightly  lift  the  porcelain  lid  in  order  to  reach  the  interior  of 
the  clay  cell.  The  clay  cells  require  emptying  entirely  only 
when  the  battery  is  not  to  be  used  for  some  time  or  when  it  is 
to  be  cleaned,  which  has  to  be  done  once  in  a  while.  When 
the  exciting  fluid  in  the  outer  cells  has  become  ineffective,  it 
has  to  be  replaced  by  a  fresh  supply.  How  often  the  battery 
has  to  be  cleansed  and  how  often  the  exciting  fluid  has  to  be 
renewed,  depends  of  course  on  the  length  of  time  the  battery 
is  in  use. 

The  efficacy  of  the  battery  can  be  still  further  increased  by 
keeping  the  exciting  fluid  in  the  exterior  cells  in  constant 
circulation,  which  is  effected  by  the  following  arrangement: 
Each  of  the  two  end  cells  of  the  battery  is  connected  with  a 


48  ELECTRO-DEPOSITION   OF   METALS. 

supply-jar  of  suitable  capacity  and  the  full  jar  of  the  two 
supply-jars  is  placed  at  a  higher,  and  the  empty  jar  at  a  lower, 
level.  By  means  of  a  screw-clip  the  discharge  and  influx  of 
the  fluid  are  so  regulated  that  the  latter  always  stands  at  the 
same  level.  When  the  upper  jar  is  empty,  the  position  of  the 
jars  is  reversed.  By  now  placing  the  two  supply-jars  in  a  tub 
containing  ice  and  thus  constantly  cooling  the  circulating  ex- 
citing fluid,  the  heating  of  the  elements  which  otherwise  con- 
stantly takes  place  is  avoided,  and  the  battery  can  be  kept 
working  for  a  longer  time  without  interruption. 

The  ordinary  Oppermann  element,  7.87  inches  high,  has  a 
tension  of  1.85  to  nearly  2  volts.  The  current  strength  meas- 
ured on  the  open  element  by  means  of  the  spiral  ammeter  is 
15  to  20  amperes.  The  quantity  of  oxyhydrogen  gas  evolved, 
measured  by  the  voltmeter,  amounts  to  about  20  ccm.  per 
minute. 

Thus  far  we  have  followed  the  statements  of  the  inventor 
himself.  The  element  has  not  yet  been  thoroughly  tested  in 
practice,  and  while  it  must  be  admitted  that  nitric  acid  con- 
taining molybdic  acid  exerts  greater  depolarizing  action  than 
either  nitric  or  chromic  acid  by  itself,  it  would  seem  to  us  that 
cleansing  the  glass-jars  of  the  depolarizing  fluid  oozing  through 
is  nearly  as  laborious,  and  consumes  as  much  time,  as  empty- 
ing the  ordinary  Bunsen  elements. 

The  Leclanche  element  (zinc  and  carbon  in  sal  ammoniac 
solution  with  manganese  peroxide  as  a  depolarizer)  need  not 
be  further  described,  it  not  being  adapted  for  regular  use  in 
electro-plating.  It  is  in  very  general  use  for  electric  bells,  its 
great  recommendation  being  that,  when  once  charged,  it  retains 
its  power  without  attention  for  several  years. 

Lallande  and  Chaperon  have  introduced  a  copper  oxide 
element,  shown  in  Fig.  15,  which  possesses  several  advan- 
tages. It  consists  of  the  outer  vessel  G,  of  cast-iron  or  cop- 
per, which  forms  the  negative  pole  surface,  and  to  which  the 
wire  leading  to  the  anodes  is  attached,  and  a  strip  of  zinc,  Z, 
coiled  in  the  form  of  a  spiral,  which  is  suspended  from  an  ebonite 


GALVANIC    ELEMENTS. 


49 


cover  carrying  a  terminal  connected  with  the  zinc.  The  her- 
metical  closing  of  the  vessel  G  by  the  ebonite  cover  is  effected 
by  means  of  three  screws  and  an  intermediate  rubber  plate. 
Upon  the  bottom  of  the  vessel  G  is  placed  a  3  to  4  inch  deep 
layer  of  copper  oxide,  O,  and  the  vessel  is  filled  with  a  solution 
of  50  parts  of  caustic  potash  in  100  of  water.  When  the  circuit 
is  closed,  decomposition  of  water  takes  place,  the  oxygen  which 
appears  on  the  zinc  forming  with  the  latter  zinc  oxide,  which 
readily  dissolves  in  the  caustic  potash  solution,  while  the 

FIG.  15. 


hydrogen  is  oxidized  with  the  simultaneous  reduction  of  copper 
oxide  to  copper.  When  the  element  is  open,  i.  e.y  the  circuit 
not  closed,  neither  the  zinc  nor  the  copper  oxide  is  attacked, 
and  hence  no  local  action  nor  any  consumption  of  material 
takes  place.  The  electro-motive  force  of  this  element  is  0.98 
volt,  and  its  internal  resistance  very  low.  It  is  remakably  con- 
stant, and  is  well  adapted  for  electro-plating  purposes  by  using 
two  of  them  for  one  Bunsen  element.  The  following  rules 
have  to  be  observed  in  its  use.  It  is  absolutely  necessary  that 
the  ebonite  cover  should  hermetically  close  the  vessel  G,  as 
otherwise  the  caustic  potash  solution  would  absorb  carbonic 
4 


50  ELECTRO-DEPOSITION   OF   METALS. 

acid  from  the  air,  whereby  carbonate  of  potash  would  be 
formed,  which  would  weaken  the  exciting  action  of  the  solu- 
tion. Fnrther,  the  vessel  G  forming  the  one  pole  must  be  in- 
sulated from  the  other  as  well  as  from  the  ground,  as  otherwise 
a  loss  of  current  or  defective  working  would  be  the  conse- 
quence. 

The  regeneration  of  the  cuprous  oxide  or  metallic  copper 
formed  by  reduction  from  the  cupric  oxide  to  cuprous  oxide,  re- 
quires it  to  be  subjected  to  calcination  in  a  special  furnace. 
The  expense  connected  with  this  operation  is,  however,  about 
the  same  as  that  of  procuring  a  fresh  supply  of  cupric  oxide. 
Lallande  himself,  as  well  as  Edison,  endeavored  to  bring  the 
pulverulent  cupric  oxide  into  compact  plates,  but  the  regenera- 
tion of  these  plates  was  still  more  troublesome.  By  treatment 
with  various  chemical  agents,  Dr.  Bottcher,  of  Leipsic,  has  suc- 
ceeded in  producing  porous  plates  of  cupric  oxide  which,  after 
subsequent  reduction  by  absorption  of  oxygen  from  the  air, 
can  be  readily  re-oxidized  to  cupric  oxide,  but  as  far  as  we 
know,  elements  with  these  plates  have  not  yet  been  intro- 
duced into  commerce. 

Umbreit  &  Matthes  bring  into  commerce  an  element  known 
as  cupron  element,  which  is  an  improved  Lallande  element,  and 
in  which  the  cupric  oxide  is  also  brought  into  the  form  of 
plates.  A  square  glass  vessel  or  vat  with  a  ground  edge 
and  closed  with  a  hard  rubber  lid  contains  two  zinc  plates,  and 
between  the  latter  the  porous  cupric  oxide  plate.  The  glass 
vessel  is  filled  with  lye  containing  20  per  cent,  of  caustic  soda, 
and  the  current  is  delivered  through  two  clamps  on  the  outside 
of  the  lid.  According  to  Umbreit  and  Matthes'  statements  the 
reduced  positive  pole  plates  are  regenerated,  that  is,  re-oxidized 
to  cuprous  oxide  by  rinsing  in  water  and  allowing  them  to 
remain  in  a  warm  place  for  20  to  24  hours,  so  that  it  is  only 
necessary  to  replace  the  soda  lye  saturated  with  zinc  oxide. 
The  electro-motive  force  of  the  element  is  0.8  volt;  the  normal 
current-strength,  according  to  the  size  of  the  elements  I,  2,  4 
and  8  amperes.  Like  the  Lallande  element,  this  element  works 
without  odor. 


GALVANIC    ELEMENTS.  51 


The  elements  of  Marie,  Davy,  Niaudet,  Duchemin,  Sturgeon, 
Trouville,  and  others  being  of  little  practical  value,  may  be 
passed  over. 

Duns 's  potash  element.  On  account  of  its  great  electro- 
motive force  (1.6  volts)  and  slight  internal  resistance,  this  ele- 
ment would  be  well  adapted  for  electro-plating  purposes,  if 
depolarization  were  effected  more  rapidly  than  is  actually  the 
case.  Its  construction  is  as  follows :  In  a  glass  vessel  stands  a 
carbon  cylinder  closed  below,  and  in  the  centre  of  the  carbon 
cylinder  a  clay  cell.  The  space  between  the  clay  cell  and  the 
interior  wall  of  the  carbon  cylinder  is  filled  five-sixths  full  with 
pieces  of  carbon.  In  the  clay  cell  stands  an  amalgamated  strip 
of  zinc  or  zinc  cylinder  to  which  the  conducting  wires  are 
soldered,  the  place  of  soldering,  as  well  as  the  wire  as  far  as  it 
comes  in  contact  with  the  fluid,  being  covered  with  gutta- 
percha.  The  edge  of  the  carbon  cylinder  is  coated  with 
paraffine  and  carries  the  pole  binding-screw.  The  filling  of 
the  element  is  effected  by  laying  potassium  permanganate  in 
crystals  upon  the  layer  of  carbon  between  the  clay  and  carbon 
cylinders,  and  pouring  a  solution  of  I  part  of  pure  caustic 
potash  in  2  of  water  into  the  clay  cell,  the  pouring  being  con- 
tinued until  the  fluid  runs  over  the  clay  cell  upon  the  potassium 
permanganate  and  the  layer  of  carbon,  and  finally  fills  the  outer 
vessel  up  to  about  the  breadth  of  two  fingers  from  the  edge. 
The  action  of  the  element  is  as  follows :  When  the  element  is 
closed  decomposition  of  water  takes  place,  the  oxygen  com- 
bining with  the  zinc  to  form  zinc  oxide,  which  is  dissolved  by 
the  potash  lye,  while  the  hydrogen  is  oxidized  on  the  positive 
pole  by  the  potassium  permanganate.  The  latter,  to  be  sure, 
contains  much  oxygen,  and  acts  very  energetically,  but  as  it 
diffuses  very  slowly,  depolarization,  i.  e.,  the  removal  of  the 
hydrogen,  is  not  so  quickly  effected  as,  for  instance,  in  the 
Bunsen  element,  where  the  nitric  acid  rapidly  diffuses.  Hence 
with  a  slight  external  resistance,  for  instance,  baths  where  the 
element  has  to  furnish  large  quantities  of  current,  the  electro- 
motive force  sinks  very  rapidly  and  with  it  the  current  strength, 


ELECTRO-DEPOSITION    OF   METALS. 


FIG.  1 6. 


and,  therefore,  the  element  is  only  suitable  for  electro-plating 
purposes  when  a  current  need  only  for  a  short  time  be  pro- 
duced, but  not  for  permanent  work.  In  the  first  case  it  offers 
the  advantage  of  being  always  ready  for 
use,  evolving  no  vapors,  and  when  not 
in  use  consuming  no  material.  It  is 
prudent  to  protect  this  element  from  the 
action  of  the  carbonic  acid  of  the  air  by  a 
close  cover. 

The  element  shown  in  Fig.  16  has 
been  patented  in  Germany,  and  is  de- 
scribed by  Knaffe  and  Kiefer,*  of  Vienna, 
as  follows :  The  element  consists  of  a 
combination  of  zinc  and  carbon.  The 
zinc  plate  is  g\  inches  long,  4f  inches 
wide,  and  of  the  thickness  of  pasteboard. 
It  is  amalgamated  according  to  a  new 
process.  It  is  placed  between  two  car- 
bon plates  of  equal  size,  the  surface  of 
which  is  twice  that  of  the  zinc.  The 
carbon  plates  are  connected  with  the  con- 
ducting wires  in  such  a  manner  as  to  pre- 
vent oxidation  of  the  binding-screws  and 
to  secure  constant  contact.  The  zinc 
plate  is  suspended  in  a  neutral  salt  solu- 
tion in  a  clay  cell,  the  space  between  the 
latter  and  the  carbon  plates  being  filled 
with  pieces  of  carbon.  The  consumption 

of  zinc  is  very  small.  The  principal  advantage  of  this  new  ele- 
ment is,  however,  the  depolarizing  fluid  of  peculiar  composition 
and  powerful  effect. 

The  element  has  an  electro-motive  force  of  1.9  volts,  an  in- 
ternal resistance  of  0.17  ohm,  and  a  constancy  such  as  seldom 
is  attained  with  primary  elements,  I  volt  ampere  lasting  for  100 
hours. 


*  Neueste  Erfindungen  und  Erfahrungen,  vol.  xviii,  p.  308. 


GALVANIC    ELEMENTS. 


53 


We  will  add  a  few  words  in  regard  to  plunge  or  bichromate 
batteries.  They  consist  of  a  number  of  separate  voltaic  cells 
connected  so  as  to  form  a  single  cell  or  electric  source,  and  the 
plates  of  which  are  so  supported  as  to  be  capable  of  being 
simultaneously  placed  in  or  removed  from  the  exciting  fluid. 
For  our  purposes  it  will  suffice  to  mention  the  Bunsen  plunge 
battery,  shown  in  Fig.  17.  For  constructive  reasons  only  one 
fluid  is  used,  into  which  the  zinc  as  well  as  the  carbon  plates 

FIG.  17. 


dip,  a  solution  of  chromic  acid  prepared  by  dissolving  10  parts 
of  bichromate  of  potash  and  \  part  of  mercuric  sulphate  in  100 
parts  of  water,  and  adding  18  parts  of  pure  concentrated  sul- 
phuric acid,  being  employed.  More  advantageous  is  a  solu- 
tion of  chromic  acid  in  the  form  of  powder  in  water,  in  the  pro- 
portion of  i  15,  for  the  same  reason  as  given  on  p.  41. 

Fig.  1 8  shows  a  bichromate  battery  as   constructed  by  Fein. 
Into  the  6  element-vessels  standing  in  two  rows  in  the  wooden 


54 


ELECTRO-DEPOSITION   OF   METALS. 


box  M  dip  the  zinc  and  carbon  plates,  which  are  secured  to 
wooden  cross-pieces  provided  with  handles,  and  may  be  main- 
tained at  any  desired  height  by  the  notch  e  in  the  standard  G. 
According  to  the  current-strength  required,  the  plates  are  allowed 
to  dip  in  more  or  less  deeply. 

FIG.  1 8. 


Fig.  19  shows  a  bichromate  battery  as  constructed  by  Keiser 
&  Schmidt. 

In  using  the  above-mentioned  chromic  acid  solution,  which 
has  been  recommended  by  Bunsen,  the  elements  at  first  develop 
a  very  strong  current,  which,  however,  in  a  comparatively  short 
time  becomes  weaker  and  weaker.  The  current-strength  can  be 
increased  by  adding  at  intervals  a  few  spoonfuls  of  pulverized 
chromic  acid  to  the  chromic  acid  solution,  which,  however, 
finally  remains  without  effect,  when  the  battery  has  to  be  freshly 
filled.  Hence,  these  batteries  are  not  suitable  for  electro- 
plating operations  requiring  a  constant  current  for  some  time. 


GALVANIC    ELEMENTS. 


55 


For  temporary  use,  for  instance,  by  gold-workers  and  others, 
for  gilding  or  silvering  small  articles,  the  bottle-form  of  the 
bichromate  element  (Fig.  20)  may  be  advantageously  em 


FIG.  19. 


FIG.  20. 


ployed.  In  the  bottle  A  two  long  strips  of  carbon]united  above 
by  a  metallic  connection  are  fastened  parallel  to  one  another 
to  a  vulcanite  stopper,  and  are  there  connected  with  the  binding- 
screw  ;  these  form  the  negative  element,  and  pass  to  the  bottom 
of  the  bottle.  Between  them  is  a  short  thick  strip  of  zinc  at- 
tached to  a  brass  rod  passing  stiffly  through  the  centre  of  the 
vulcanite  cork,  and  connected  with  the  binding-screw.  The 
zinc  is  entirely  insulated  from  the  carbon  by  the  vulcanite,  and 
may  be  drawn  out  of  the  solution  by  means  of  the  brass  rod  as 
soon  as  its  services  are  no  longer  required. 

This  bichromate  element  is  excellent  for  purposes  requiring 
strong  currents,  where  long  action  is  not  necessary.  As  this 
element  readily  polarizes,  it  cannot  be  advantageously  employed 
continuously  for  any  considerable  period  of  time.  It  becomes 
depolarized,  however,  when  left  for  some  time  on  open  circuit. 
The  element  gives  an  electro-motive  force  of  about  1 .9  volts. 


ELECTRO-DEPOSITION    OF   METALS. 


In  Stoehrer's  battery  (Fig.  21)  two  acids,  dilute  sulphuric 
acid  and  concentrated  nitric  acid,  are  used.  The  porous  clay 
cell  is  omitted,  the  massive  carbon  cylinders  K,  K,  etc.,  being 
provided  with  a  cavity  reaching  almost  to  the  bottom,  which  is 
filled  with  sand  and  nitric  acid.  The  contact  of  the  carbon  and 
zinc  cylinders  is  prevented  by  glass  beads  imbedded  in  the 
carbon  cylinders. 


FIG.  21. 


FIG.  22. 


Fig.  22  shows  a  plunge  battery  manufactured  by  Dr.  G.  Lang- 
bein  &  Co.,  at  Leipzig-Sellerhausen,  Germany,  the  details  of 
which  will  readily  be  understood  without  further  description. 
The  zinc  plates  dip  into  the  diaphragms  which  are  filled  with  a 
mixture  of  26  Ibs.  of  water  and  2  Ibs.  of  sulphuric  acid  free 
from  arsenic  in  which  2f  ozs.  of  amalgamating  salt  have  pre- 
viously been  dissolved.  The  carbon  plates  dip  into  the  glass 


GALVANIC    ELEMENTS.  57 

vessels,  which  contain  a  solution  of  commercial  crystallized 
chromic  acid  in  water  in  the  proportion  of  I  part  acid  to  9 
water.  In  place  of  this  pure  chromic  acid  solution  the  follow- 
ing mixture  may  also  be  used : 

Water  10  parts  by  weight,  sodium  dichromate  0.75  part  by 
weight,  pure  sulphuric  acid  of  66°  Be.  1.5  parts  by  weight. 

This  solution  shows  no  inclination  towards  crystallization. 
In  the  illustration  only  two  elements  are  combined  to  a  battery, 
but  in  the  same  manner  a  plunge  battery  of  four  and  eight  ele- 
ments may  be  constructed,  the  separate  elements  of  which  may 
all  be  coupled  parallel,  as  well  as  one  after  the  other,  and  in 
mixed  groups. 

B.   THERMO-ELECTRIC  PILES. 

Though  thermo-electric  piles  are  only  used  in  isolated  cases 
for  electro  plating  operations,  for  the  sake  of  completeness 
their  nature  and  best-known  forms  will  be  briefly  mentioned. 

In  the  year  1822,  Professor  Seebeck,  of  Berlin,  discovered  a 
new  source  of  electricity,  namely,  inequality  of  temperature  and 
conducting  power  in  different  metals,  or  in  the 
same  metal  in  different  states  of  compression  FlG>  23> 

and  density.  When  two  pieces  of  different 
metals,  connected  together  at  each  end,  have 
one  of  their  joints  more  heated  than  the  other, 
an  electric  current  is  immediately  set  up.  Of 
all  the  metals  tried,  bismuth  and  antimony 
form  the  most  powerful  combination. 

In  Fig.  23  Bm  represents  a  bar  of  bismuth, 
and  mS  a  bar  of  antimony  soldered  to  the  bis- 
muth bar.     By  leading  wires  from  B  and  5  to 
a  galvanoscope,   G,  and  heating  the  point  of 
junction  m,  the  needle  of  the  galvanoscope  is 
deflected.     From  this  it  may  be  concluded  that  an  electric  cur- 
rent circulates  in  the  closed   circuit   GB  mS  G.     By  a  closer 
examination  the  direction  of  the  current  may  be  recognized,  it 
flowing  on  the  heated  point  of  junction  from  the  bismuth  to  the 


ELECTRO-DEPOSITION   OF   METALS. 


antimony,  and  in  the  connecting  wire  of  the  ends  of  the  rods 
which  remain  cold,  from  the  antimony  to  the  bismuth.  The 
current  is  the  stronger  the  greater  the  difference  in  the  tem- 
perature of  the  point  of  junction  and  the  free  ends  of  the  bars. 
Hence  the  electric  current  will  be  especially  strong  when  the 
place  of  junction  is  heated  and  the  ends  B  and  5"  are  at  the 
same  time  cooled  off.  A  combination  as  above  described  is 
called  a  thermo-electric  couple,  and  the  electricity  obtained  in 
this  manner  thermo-electricity.  By  a  suitable  combination  of 
several  or  many  of  such  couples,  a  thermo-electric  pile  is  ob- 
tained. 

Noe's  thermo-electric  pile  (Fig.  24)   consists  of   a  series  of 

FIG.  24. 


small  cylinders,  composed  of  an  alloy  of  36^2  parts  of  zinc  and 
62  y2  parts  of  antimony  for  the  positive  element,  and  stout 
German  silver  as  the  negative  element.  The  junctions  of  the 
elements  are  heated  by,  small  gas-jets,  and  the  alternate  junc- 
tions are  cooled  by  the  heat  being  conducted  away  by  large 
blackened  sheets  of  thin  copper.  A  pile  of  twenty  pairs  has  an 
electro-motive  force  of  1.9  volts. 

Clamond's  thermo-electric  pile  (Fig.  25)  consists  of  an  alloy 
of  2  parts  antimony  and  I  of  zinc  for  the  negative  metal,  while 


GALVANIC    ELEMENTS. 


59 


for  the  positive  element  ordinary  tinned  sheet-iron  is  employed, 
the  current  flowing  through  the  hot  junction  from  the  iron  to 
the  alloy.  To  insure  a  good  contact  between  the  two  metals  a 
strip  of  tin-plate  is  bent  into  a  narrow  loop  at  one  end.  This 
portion  is  then  placed  in  a  mould  and  the  melted  alloy  poured 
around  it,  so  that  it  is  actually  imbedded  in  the  casting.  The 
pile  shown  in  the  illustration  consists  of  five  series,  one  placed 
above  the  other.  Each  series  has  ten  elements  grouped  in  a 
circle,  and  is  insulated  from  the  succeeding  series  by  a  layer  of 

FIG.  25. 


cement,  composed  of  powdered  asbestos  moistened  with  a  solu- 
tion of  potassium  silicate.  With  the  consumption  of  about  6^ 
cubic  feet  of  gas  per  hour,  such  a  pile  precipitates  0.7  oz.  of 
copper,  which  corresponds  to  an  electro-motive  force  of  about 
17  amperes. 

Hauck '  s  thermo-electric  pile. — An  essential  defect  of  Clamond's 
thermo-electric  pile  consists  in  that  the  junctions  of  the  dissimilar 
metals  are  subjected  to  ready  destruction  by  being  exposed  to 
the  direct  action  of  the  flame.  Further,  it  is  very  difficult,  or 
at  least  inconvenient,  to  make  repairs,  since  in  such  a  case  it 
may  become  necessary  to  take  the  entire  pile  apart.  Hauck 


6o 


ELECTRO- DEPOSITION    OF   METALS. 


has  successfully  overcome  these  defects  by  adopting  the  princi- 
ple of  indirect  heating,  as  well  as  by  giving  the  couples  a  more 
suitable  form  and  by  improving  the  alloy.  The  couples  form 
four-sided  wedges,  to  which  are  attached  cast-iron  pieces  that 
transfer  the  heat  of  the  gas-burner  to  the  couples.  The  electro- 
motive force  of  a  single  couple  is  ^  that  of  a  Daniell  element. 
Fig.  26  shows  a  combination  of  two  piles  standing  upon  a  com- 

FIG.  26. 


mon  plate,  one  of  the  piles  being  given  in  cross-section.  The 
glass-vessel  H,  with  the  tube,  B,  G,  R,  I,  serves  as  a  regulator 
for  the  gas-pressure.  The  pile  shown  in  the  illustration  serves 
for  the  production  of  metallic  deposits  on  a  small  scale,  especi- 
ally for  analytical  examinations.  Hauck,  however,  also  furnishes 
combinations  of  three  larger  piles. 

Gulcher  s  thermo-electric  pile,  invented  in  1890,  is  shown  in 
Fig.  27.  It  is  arranged  for  gas-heating,  and  with  a  constant 
supply  of  gas  requires  a  pressure-regulator.  The  negative 


GALVANIC   ELEMENTS. 


6l 


electrodes  consist  of  nickel  and  the  positive  electrodes  of  an 
antimony  alloy,  the  composition  of  which  is  kept  secret.  The 
negative  nickel  electrodes  have  the  form  of  thin  tubes  and  are 
secured  in  two  rows  in  a  slate  plate,  which  forms  the  termina- 
tion of  a  gas  conduit  with  a  U-shaped  cross-section  beneath  it. 
Corresponding  openings  in  the  slate  plate  connect  the  nickel 
tubes  with  the  gas  conduit,  the  latter  being  connected  by  means 
of  a  rubber  tube  with  the  pipe  supplying  the  gas.  Thus  the 
gas  first  passes  into  the  conduits,  next  into  the  nickel  tubes,  and 
leaves  the  latter  through  six  small  holes  in  a  soap-stone  socket 
screwed  in  the  end  of  each  tube.  On  leaving  these  sockets  the 
gas  is  ignited  and  the  small  blue  flames  heat  the  connecting 
piece  of  the  two  electrodes.  This  connecting  piece  consists  of 

FIG.  27. 


a  circular  brass  plate  placed  directly  over  the  soap-stone  socket. 
One  end  of  it  is  soldered  to  the  nickel  tube,  while  the  other 
ends,  towards  the  top,  in  a  socket  in  which  are  cast  the  positive 
electrodes.  The  latter  have  the  form  of  cylindrical  rods  with 
lateral  angular  prolongations.  To  the  ends  of  these  prolonga- 
tions are  soldered  long  copper  strips  secured  in  notches  in  the 
slate  plate.  They  serve  partially  for  cooling  off  and  partially 
for  connecting  the  couples.  For  the  latter  purpose  each  copper 
strip  is  connected  by  a  short  wire  with  the  lower  end  of  the 
nickel  tube  belonging  to  the  next  couple.  When  the  pile  is  to 
be  used,  the  gas  is  ignited  in  one  place,  the  ignition  spreading 
rapidly  through  the  entire  series  of  couples.  In  about  10  min- 


62  ELECTRO- DEPOSITION    OF   METALS. 

utes  the  junctions  of  the  metals  have  attained  their  highest 
temperature  and  the  pile  its  greatest  power,  which,  with  a  con- 
stant supply  of  gas,  remains  unchanged  for  days  or  weeks. 

In  view  of  the  conversion  of  the  heat  produced  by  the  com- 
bustion of  the  gas  into  electricity,  the  useful  effect  of  the  thermo- 
electric pile  can  be  considered  only  a  very  slight  one.  One 
cubic  meter  of  ordinary  coal-gas  produces  on  an  average  5200 
heat-units,  hence  200  litres  per  hour  referred  to  one  second 
i-Tfr-i-  5200  =  °-29  heat-unit.  These  correspond  to  1208 
volt-amperes,  I  volt-ampere  being  equal  to  0.00024  heat-unit. 
Hence,  in  Giilcher's  thermo-electric  pile,  which  at  present  pro- 
duces the  greatest  useful  effect,  not  much  more  than  I  per  cent. 
of  the  heat  is  utilized  in  the  entire  circuit,  and  about  ^  per 
cent,  in  the  outer  circuit. 

Although  thermo-electric  piles  may  be,  and  are  occasionally, 
used  for  electro-plating  operations,  they  cannot  compete  with 
dynamo-electric  machines  driven  by  steam,  which  as  regards 
the  consumption  of  heat  are  at  least  five  times  more  effective. 
They  can  only  be  used  in  place  of  galvanic  batteries,  they  hav- 
ing the  advantage  of  being  more  convenient  to  put  in  operation, 
more  simple,  cleanly,  odorless,  and  requiring  less  time  for 
attendance.  But,  on  the  other  hand,  their  original  cost  is  com- 
paratively large,  it  being  ten  to  twenty  times  that  of  Bunsen 
elements.  Thus,  for  instance,  Gulcher's  thermo-electric  pile 
costs  $37.50  in  Germany,  to  which  have  to  be  added  $5  for  the 
gas-pressure  regulator,  if  required. 

C.  MAGNETO-  AND  DYNAMO- ELECTRIC  MACHINES. 

It  is  a  well-known  fact  that  all  the  early  experiments  and  im- 
provements in  dynamos  were  made  with  a  view  of  perfecting 
an  electrical  machine  for  plating,  and  that  the  success  attained 
therein  was  the  forerunner  of  all  the  magnificent  dynamo 
machines  for  other  purposes  in  such  general  use. 

The  principle  of  induction  upon  which  the  dynamo-electric 
machines  are  based  has  been  explained  on  p.  23.  Faraday,  in 
1831,  made  the  important  discovery  that  by  moving  a  coil  of 


GALVANIC    ELEMENTS.  63 

wire  in  the  presence  of  a  magnet  a  current  of  electricity  was 
generated  in  the  coil,  or,  vice  versa,  by  moving  the  magnet  and 
holding  the  coil  stationary  a  like  result  was  obtained.  Thus  a 
current  of  electricity  was  produced  either  "by  moving  a  wire  in 
the  presence  of  a  stationary  magnet,  or  by  moving  a  magnet  in 
the  presence  of  a  stationary  wire. 

The  intensity  of  the  current  thus  obtained  depends  on  the 
power  of  the  magnet  and  on  the  velocity  with  which  the  mag- 
net or  coil  is  moved  through  the  magnetic  field.  Upon  these 
simple  facts  is  based  the  whole  of  the  recent  important  develop- 
ments of  electrical  science. 

Before  describing  the  various  attempts  made  to  devise  some 
mechanical  means  whereby  the  different  elements  which  pro- 
duced the  temporary  or  momentary  currents  could  be  com- 
bined, so  as  to  collect  them,  and  cause  them  to  flow  in  rapid 
succession,  the  one  after  the  other,  without  interruption,  it  will 
be  well  to  remember  that  the  necessary  elements  for  producing 
these  induced  electric  currents  are  simply  a  bar  magnet  and  an 
insulated  coil  of  wire.  It  will  also  be  well  to  remember  that 
every  magnet,  no  matter  what  its  form,  has  two  poles — a  north 
and  a  south  pole — and  each  of  these  poles  exerts  a  certain 
influence  in  its  immediate  neighborhood,  the  space  thus  affected 
being  termed  the  magnetic  field  or  the  region  of  the  lines  of  force. 
The  attraction  or  magnetic  force  of  these  lines  varies  as  the  in- 
verse ratio  of  the  square  of  the  distance ;  therefore,  the  nearer 
the  magnet  the  greater  the  intensity  of  the  magnetism.  Fara- 
day proved  that  these  lines,  which  he  designated  lines  of  force, 
showed  by  their  position  the  direction  of  the  magnetic  force, 
and  by  their  number  its  intensity.  By  passing  a  coil  of  wire 
through  this  field,  so  as  to  cause  it  to  cut,  as  it  were,  a  number 
of  these  lines  of  force,  a  current  of  electricity  will  be  generated 
in  the  coil;  and  if  it  can  be  so  arranged  that  a  number  of  these 
coils  will  pass  in  rapid  succession  through  the  magnetic  field, 
we  shall  have  a  series  of  impulses  giving  us  practically  a  con- 
tinuous stream  of  electricity. 

Thus    a    magneto-electric    or    dynamo-electric    machine    is 


64  ELECTRO-DEPOSITION   OF   METALS. 

simply  a  machine  for  the  conversion  of  mechanical  energy  into 
electrical  energy  by  means  of  magneto-electric  induction.  The 
term  dynamo-electric  machine  is  also  applied  to  a  machine  by 
means  of  which  electrical  energy  is  converted  into  mechanical 
energy  by  means  of  magneto-electric  induction.  Machines  of 
the  latter  class  are  generally  called  motors,  those  of  the  former 
generators. 

Prof.  S.  P.  Thompson  defines  a  dynamo-electric  machine  as 
follows : — 

"  A  machine  for  converting  energy  in  the  form  of  mechanical 
power  into  energy  in  the  form  of  electric  currents,  or,  vice  versa, 
by  the  operation  of  setting  conductors  (usually  in  the  form  of 
coils  of  copper  wire)  to  rotate  in  a  magnetic  field,  or  by  vary- 
ing a  magnetic  field  in  the  presence  of  conductors." 

The  term  dynamo  was  first  applied  to  such  machines  because 
of  the  form  in  which  this  machine  first  appeared,  viz.,  the  series- 
wound  machine.  It  was  self-acting,  or  required  no  excitement 
other  than  what  it  received  by  the  rotation  of  its  armature  in 
the  field  of  its  magnets,  or,  indeed,  in  the  field  of  the  earth. 

A  dynamo-generator,  or  a  dynamo-electric  machine  proper, 
consists  of  the  following  parts:  — 

1.  The  revolving  portion,  usually  the  armature,  in  which  the 
electro-motive  force  is  developed  which  produces  the  current. 

2.  The  field  magnets,  which  produce  the  field  in  which  the 
armature  revolves. 

3.  ^hs.  pole  piece S)  or  free  terminals  of  the  field  magnets. 

4.  The  commutator,  by  which  the  currents  developed  in  the 
armature  are  caused  to  flow  in  one  and  the  same  direction.     In 
alternating  machines  and  in  some  continuous  current  dynamos 
this  part  is  called  the  collector,  and  does  not  rectify  the  currents. 

5.  The  collecting  brushes,  that  rest  on  the  commutator  cylinder, 
and  take  off  the  current  generated  in  the  armature. 

The  number  of  such  dynamo  machines  is  legion.  In  each 
case  the  arrangement  of  the  armature  of  the  magnets  and  of  the 
commutators  is  varied,  but  the  principle  is  always  the  same — 
coils  of  insulated  wire  being  caused  to  cut  through  magnetic 
fields,  as  already  explained. 


GALVANIC    ELEMENTS.  65 

The  first  attempt  to  devise  an  electrical  machine  was  made 
by  Pixii,  who,  in  1832,  constructed  a  machine  consisting  of  a 
permanent  magnet,  which  he  caused  to  revolve  in  front  of  the 
iron  cores  of  a  pair  of  bobbins,  forming  an  electro-magnet. 
This  invention  was  improved  by  other  workers  in  the  field  of 
science,  especially  by  Saxton  and  Clarke,  both  of  whom  suc- 
ceeded in  producing  very  useful  electric  generators,  in  which  the 
mechanical  arrangement  is  the  reverse  of  that  in  Pixii's — i.  e., 
the  magnets  are  fixed  and  the  coils  of  wire  movable.  And  it  is 
on  this  plan  that  all  the  subsequent  machines  have  been  con- 
structed, as  affording  better  results  than  where  the  coils  are 
stationary  and  the  magnets  movable. 

A  great  improvement  was  made  in  1857,  by  Dr.  W.  Siemens, 
of  Berfin.  It  consisted  essentially  in  a  new  form  of  armature, 
which,  owing  to  its  simplicity  and  cheapness,  is  still  used  for 
many  purposes,  especially  for  electro-plating  and  laboratory 
work.  It  is  composed  of  a  cylinder  of  iron  in  which  deep  longi- 
tudinal grooves  are  cut  resembling  in  section  the  letter  H.  In 
these  grooves  is  wound  lengthwise  a  single  coil  of  wire,  the  two 
ends  of  which  being  joined  to  a  split  tube  of  copper  on  the  axle 
form  the  commutator,  from  which  the  current  is  taken  off  by 
brushes  or  springs  rubbing  against  it.  By  this  longitudinal  arma- 
ture the  advantage  is  gained  of  cutting  the  greatest  number  of 
lines  of  force  when  rotated  between  the  poles  of  a  series  of  ad- 
jacent magnets. 

One  of  the  most  important  inventions  for  the  construction  of 
electrical  machines  is  the  ring  conductor  by  Pacinotti  (1860). 
With  the  use  of  this  ring  conductor  continuous  currents  of  the 
same  direction  can  be  produced  without  the  assistance  of  a 
commutator. 

Next  in  order  comes  the  important  discovery  made  simulta- 
ously,  but  independently,  by  Dr.  W.  Siemens  and  Sir  C.  Wheat- 
stone — a  discovery  which  marks  the  transition  of  the  magneto- 
electric  machine  to  that  type  most  in  practice  at  present — the 
dynamo  machine,  called  for  convenience  the  dynamo.  What 
Siemens  and  Wheatstone  discovered  was  this :  That  a  current 
5 


66  ELECTRO-DEPOSITION   OF   METALS. 

of  electricity  could  be  generated  in  the  coils  of  the  armature 
by  the  feeble  residual  magnetism  in  the  iron  cores  of  the  elec- 
tro-magnets, and  that  by  passing  this  feeble  current  round  the 
magnets  their  magnetism  would  be  strengthened,  which  in  turn 
would  produce  a  stronger  current  in  the  armature,  and  this  cur- 
rent would  again  react  on  the  magnets,  rendering  them  more 
powerful,  this  action  going  on  until  the  limit  of  saturation  is  at- 
tained. For  it  must  be  understood  that  this  mutual  accumulation 
cannot  go  on  indefinitely,  the  magnetism  in  the  iron  cores  can- 
not be  intensified  beyond  a  certain  point,  and  this  point  depends 
on  and  is  controlled  by  the  scientific  conditions  on  which  the 
machine  is  constructed. 

Machines  constructed  on  this  principle  are  called,  as  stated, 
dynamo  machines,  to  distinguish  them  from  those  previously 
used  in  which  the  magnets  were  permanently  magnetized,  thus 
causing  the  division  of  electric  generators  into  two  great  classes, 
viz.,  magneto  and  dynamo  machines,  which  are  subdivided  into 
two  varieties — one  called  the  continuous  current  machine,  fur- 
nishing currents  in  the  same  direction,  and  the  other  the  alter- 
nating current  machine,  wherein  the  current  is  rapidly  reversed 
or  its  direction  changed  many  times  a  minute. 

An  essential  difference  between  continuous  and  alternating 
current  machines  is  that  the  former  may  be  self-exciting, 
whereas  the  latter  must  have  a  separate  excitor  or  must  be  a 
magneto  machine.  The  cores  of  the  electro-magnets,  it  may 
be  mentioned,  are  of  cast  iron,  in  which  there  is  always  a  feeble 
residual  magnetism.  It  is  also  easier  to  magnetize  iron  than 
steel,  although,  when  the  latter  is  once  magnetized,  it  retains 
its  magnetism  for  an  indefinite  period. 

It  is  not  within  the  province  of  this  work  to  describe  in  detail 
all  the  forms  of  dynamos,  it  being  sufficient  for  our  purpose  to 
discuss  those  which  are  adapted  to  and  are  used  for  electro- 
plating uses.  If  we  mention  the  Gramme  machine  first,  it  is 
not  because  it  is  superior  to  other  machines,  but  because  M. 
Gramme,  its  inventor,  was  the  first  to  utilize  the  idea  suggested 
by  Dr.  Pacinotti,  of  using  an  iron  ring  as  a  revolving  electro- 


GALVANIC    ELEMENTS.  6/ 

magnet,  which,  in  place  of  having  fixed  revolving  poles,  had 
poles  which  traveled  continuously  through  the  whole  circum- 
ference of  the  ring. 

Fig.  28  shows  the  Gramme  armature  in  such  a  way  as  to 
allow  its  construction  to  be  seen.  The  core  or  centre  of  the 
ring  consists  of  a  bunch  of  soft  iron  wires.  The  wire  system 
wound  about  the  core  is  formed  of  different  spools,  the  initial 
wire  of  which  is  soldered  to  the  terminal  wire  of  the  neighboring 
spool,  so  that  all  the  spools  of  the  ring  form  a  single  uninter- 
rupted conductor.  The  soldered  places  lie  all  on  one  side  of 

FIG.  28. 


the  ring,  and  are  fastened  to  flat  copper  strips  bent  at  right 
angles  and  insulated  from  one  another  by  a  non-conducting 
mass  which  forms  the  commutator  through  which  the  axle 
passes.  The  armature  revolves  between  the  poles  of  the  electro- 
magnets secured  to  the  sides  of  the  machine,  as  shown  in  Fig. 
29.  As  the  ring  is  revolved  a  current  is  generated  and  flows 
out  with  every  change  in  its  position.  The  current  so  made  is 
carried  out  by  wire  brushes  which  press  upon  the  terminal 
plates  of  the  wires  in  the  ring. 

In  the  modern  Gramme  dynamos  (Fig.  30)  for  galvano- 
plastic  purposes,  which  have  to  furnish  a  considerable  volume 
of  current  of  slight  electro-motive  force,  the  inducting  magnets 
are  surrounded  by  broad  copper  bands  instead  of  being  wound 


68 


ELECTRO-DEPOSITION    OF   METALS. 


about  with  copper  wire,  and  the  armature  is  built  up  of  stout 
copper  rods,  because  the  less  resistance  the  copper  windings 
have  the  greater  the  volume  of  current  which  is  produced,  while, 
vice  versa,  the  tension  increases  with  their  resistance.  Hence, 
machines  for  electro-plating  purposes,  which  have  to  furnish 
quantities  of  current  of  slight  tension,  are  wound  about  with 

FIG.  29. 


stout  copper  wire,  while  those  for  illuminating  purposes,  which 
must  furnish  currents  of  high  tenison,  are  wound  about  with 
thin  copper  wire.  For  this  reason  machines  constructed  for 
galvano-plastic  use  and  for  nickeling,  coppering,  brassing,  etc., 
are  not  suitable  for  illuminating  purposes,  and  vice  versa,  ma- 
chines constructed  for  electric  lighting  cannot  suitably  be  em- 
ployed for  plating  purposes. 

A  disadvantage  of  the  Gramme  machine  is  that  the  only  por- 
tion of  the  copper  windings  on  the  outside  of  the  ring  conductor 


GALVANIC    ELEMENTS. 


69 


is  in  the  magnetic  field  of  the  poles  of  the  electro-magnets,  so 
that  only  a  comparatively  small  portion  of  the  inductor  is  ex- 
posed to  the  inductive  action  of  the  magnets.  Hence,  in  order 
to  furnish  correspondingly  strong  currents,  the  ring  inductor 
must  revolve  very  rapidly,  the  three  sizes  or  numbers  of  Gramme 
machines  mostly  employed  for  galvano-plastic  purposes  making 

FIG.  30. 


in  fact  from  1500  to  2000  revolutions  per  minute,  whereby  the 
bearings  are  more  rapidly  worn  out  than  with  machines  running 
at  less  speed,  and,  besides,  more  power  is  consumed. 

This  evil  led  S.  Schuckert,  of  Nuremberg,  to  construct  a  ma- 
chine in  which  Ziflat  ring  is  successfully  used  as  an  inductor, 
which  stands  almost  entirely  under  the  inductive  influence  of 
the  electro-magnets.  Schuckert's  flat  ring  machine  is  shown  in 
Fig.  31.  The  core  of  the  machine  consists  of  thin  sheet  rib- 
ands insulated  one  from  another,  whereby  greater  solidity  is 


70  ELECTRO-DEPOSITION   OF   METALS. 

attained.  The  commutator  and  brushes  are  similar  to  those  of 
the  Gramme  machine.  The  number  of  revolutions  varies  for 
the  different  size  machines  from  500  to  1500  per  minute.  It  is 
almost  noiseless  in  action  and  is  exceedingly  well  constructed. 
The  formation  of  sparks  on  the  contact-surface  of  the  brushes 
with^the  commutator  is  scarcely  perceptible,  which  secures  the 
durability  of  the  latter. 

FIG.  31. 


Fein,  offStuttgart,  has  endeavored  to  overcome  the  defect  of 
the  Gramme  machine  in  a  different  manner.  In  his  machines 
thejpolar  extensions  of  the  magnets  M  and  M1  (Fig.  32)  are 
elongated  to  a  sort  of  drum,  A  A,  which  leads  into  the  inter- 
ior of  the  inductor  ring,  whereby  the  greater  portion  of  the 
windings  is  aiso  brought  into  the  magnetic  fields  of  the  electro- 
magnets. 

Closely  resembling  the  Gramme  machine  in  its  general  out- 
line, but  differing  materially  in  construction  and  action,  is  that 
known  as'the  Brush  dynamo.  Its  armature,  though  consisting 
of  a  ring  like  that  of  Gramme's,  is  however,  differently  built  up. 
At  intervals  around  the  ring  a  number  of  transverse  grooves 
are  formed,  in  which  are  wound  the  coils  or  bobbins,  all  in  the 


GALVANIC    ELEMENTS. 


same  direction :  and  instead  of  forming  a  continuous  circuit,  as 
in  theTGramme,  each   diametrically  opposite  pair  of  coils   is 

FIG.  32. 


joined  to  each  other  by  one  end  of  each  coil,  while  the  other 
ends  of  the  pair  (i.  e.,  the  ends  conveying  the  current)  are  con- 

FIG.  33. 


nected  to  the  commutator.  Fig.  33  illustrates  the  ring,  showing 
the  opposite  coils  joined  up  as  described.  Four  coils  are  re- 
moved to  show  its  construction.  A  series  of  deep  concentric 


72  ELECTRO-DEPOSITION   OF   METALS. 

grooves  will  be  observed  formed  in  the  ring,  their  object  being 
to  reduce  the  mass  of  iron,  and  also  to  faciliate  ventilation, 
thereby  preventing  the  tendency  to  heat  while  the  machine  is 
working. 

Fig.  34  represents  the  complete  Brush  machine  set  in  motion 
by  a  Brotherhood  motor  with  three  cylinders,  the  usual  speed 
of  the  machine  being  about  750  revolutions  per  minute. 

The  machines  built  by  Siemens  &  Halske,  in  which  the  cylin- 
der-inductor invented  by  Hofner-Altenbeck  is  used,  shows  a 
different  construction  from  those  previously  described.  A  de- 

FIG.  34. 


tailed  explanation  of  the  cylinder-inductor  would  lead  us  too 
far.  It  consists  of  a  hollow  iron  cylinder,  which  revolves  with 
the  shaft,  and  about  which  the  wires  are  wound  parallel  to  the 
revolving  axis  in  such  a  manner  that  no  wire-windings  are  in 
the  interior  of  the  core  (cylinder).  The  wire  spirals  wound 
about  the  cylinder  are  divided  into  sections,  which'  are  so  con- 
nected one  with  another  as  to  form  a  single  connected  wire 
conductor.  The  terminal  wires  of  the  separate  sections  are 
connected  to  the  segments  of  the  commutator,  so  that  both  the 
currents  generated  in  the  wire  system  always  meet  from  an 
opposite  direction  in  two  portions  of  the  commutator  opposite 


('* 

GALVANIC    ELEMENTS. 


73 


to  one  another.  The  commutator  is  constructed  according  to 
the  Gramme  system,  and  has,  of  course,  as  many  segments  as 
there  are  sections  wound  upon  the  cylinder.  A  real  advantage 
of  the  machine  is  that  the  greater  portion  of  the  wire-windings 
of  the  cylinder-inductor  is  in  the  magnetic  field. 

FIG.  35. 


Fig.  35  shows  a  Siemens  &  Halske  magneto-electric  machine 
with  cylinder-inductor. 

Two  series  of  25  V-shaped  magnets  each  are  placed  above 
and  below,  so  that  their  poles  of  a  similar  name  are  opposite  to 
one  another,  the  poles  of  a  similar  name  of  the  upper  and  lower 
magnets  being  connected  one  with  another  by  arched  pieces  of 
soft  iron.  In  the  space  thus  formed  between  the  upper  and 
lower  magnets,  the  cylinder-inductor  revolves,  the  generated 
currents  being  carried  away  from  the  commutator  by  the 
brushes  R  and  R'. 

In  Siemens  &  Halske's  dynamo- electric  machines  for  electro- 
metallurgical  purposes  (Fig.  36)  the  plate  magnets  are  wound 
about  with  square  copper  rods,  in  smaller  machines  with  stout 
copper  wire,  while  instead  of  spirals  the  inductor  carries  copper 


74 


ELECTRO-DEPOSITION    OF   METALS. 


ribands,  which  are  connected  with  the  commutator  by  suitably 
bent  pieces. 

FIG.  36. 


Fig.  37  shows  the  Krottlinger  machine  constructed  by  Krott- 
linger,  of  Vienna.     It  consists  of  a  strong  iron  base,  P,  from 


which  rise  two  short  cylindrical  electro-magnets,  M  M,  which 
have  a  semicircular  shaft  on  the  upper  end  N,  and  closely 
embrace  the  ring  R.  The  standards  L  are  cast  in  one  piece 


GALVANIC    ELEMENTS. 


75 


with  the  base  P,  and  carry  the  bearing  W  W.  The  core  of  the 
ring  R  consists  of  separate  disks  of  cast-iron  arranged  alongside 
one  another  upon  the  shaft  so  as  to  form  a  massive  cylinder 
which  is  wound  about  with  stout  copper  wire.  The  inductive 
spools  of  the  ring  are  connected  by  means  of  screws  with  phos- 
phor-bronze plates  of  the  commutator  C.  In  this  dynamo  the 
current  generated  in  the  ring  does  not  pass  first  through  the 
electro-magnets,  and  then  as  working  current  into  the  con- 
ductor, but  the  greater  portion  passes  as  working  current  from 
the  brushes  B  B  into  the  conductor  to  the  baths,  while  the 
other  comparatively  smaller  portion  of  current  passes  through 
the  wrappings  of  the  electro-magnets  M  M,  and  excites  them. 
As  in  Schuckert's  machines,  a  regulator  with  resistance  coils 
may  be  inserted  in  the  circuit  of  the  current,  which  allows  of 
the  generation  of  the  current  being  controlled  within  quite  wide 
limits,  as  may  be  desired.  The  advantages  of  this  dynamo  con- 
sist in  the  large  masses  of  iron  of  short  length  with  a  large 
cross-section  of  the  co'res  of  the  electro-magnets,  the  standards 
and  base  being  made  in  one  piece,  and  in  the  durable  iron  core 
of  the  ring.  The  formation  of  sparks  is  slight. 

The  Lahmeyer  dynamo,  shown  in  Figs.  38,  39,  and  40,  in 


FIG.  38. 


cross-section,  open  side  view,  and  perspective  exterior  view, 
fulfils  the  three  principal  conditions  of  a  good  dynamo,  viz., 
great  useful  effect,  discharge  of  the  current  without  sparks,  and 


/6  ELECTRO-DEPOSITION    OF   METALS. 

solidity  of  construction.  Opposite  to  the  drum-anchor  or  drum- 
inductor  of  the  machine  stand  horizontally  two  short  and  stout 
electro-magnet  cores,  whose  ends  averted  from  the  anchor  are 
connected  by  a  thick  iron  frame  carried  above  and  below 
around  the  windings.  This  electro-magnet  frame  is  made  of 
soft  cast-iron  in  one  piece  with  the  base  of  the  machine,  so  that 
no  resistance  is  offered  to  the  lines  of  force  by  a  joint,  while  the 
large  iron  cross-sections  also  give  rise  to  but  slight  magnetic 
resistance. 

The  magnetic  field  of  the  Lahmeyer  machine  must  be  con- 
sidered as  a  magnetic  circle  in  so  far  as  the  lines  of  force  which 
are  generated  by  the  spools  in  the  iron  everywhere  contiguous 
to  them  pass  together  through  both  spools,  and  only  ramify 
outside  of  them  in  the  re-conducting  plates  B  Bf.  By  this 
favorable  disposition,  a  current  of  slight  strength  passing 

FIG.  40. 


through   the    wrappings    of   the    electro-magnets    produces    a 
strong  excitation  of  the  latter. 

The  anchor  has  the  shape  of  the  Siemens  cylinder,  but  is 
composed  of  disks  of  thin,  white  sheet-iron  insulated  one  from 
the  other  by  paper.  Several  segments  of  vulcanized  fibre,  two 
of  which  form  the  face,  serve  for  holding  the  wrappings  of  the 
anchor.  The  latter  consists  of  a  single  layer  of  stout  copper 
wire,  and  this,  in  conjunction  with  the  symmetrical  disposition 
which  excludes  the  scattering  of  the  lines  of  force  as  much  as 


GALVANIC    ELEMENTS.  77 

possible,  effects  a  discharge  of  the  current  without  sparks.  The 
space  visible  in  the  side  view  is  closed  by  perforated  plates 
secured  by  screws,  as  seen  in  Fig.  40.  This  is  a  further  ad- 
vantage of  the  machine  in  so  far  that  all  sensitive  parts  are 
protected  from  external  injury.  Like  all  cylinder  or  drum 
dynamos,  the  Lahmeyer  dynamo  requires  a  large  number  of 
revolutions  per  minute,  but  with  the  slight  weight  of  the  anchor, 
and  the  solid  construction  of  the  bearings,  there  is  but  little 
danger  of  the  rapid  wearing  out  of  the  latter. 

It  may  be  of  interest  to  give  here  a  brief  resume  of  what  may 
be  called  the  evolution  of  the  dynamos  for  plating  purposes  in 
the  United  States,  with  special  reference  to  the  machines  built 
by  the  Hanson  &  Van  Winkle  Co.,  of  Newark,  N.  J. 

The  first  machine  for  electro-plating  in  the  market  was  the 
Weston  dynamo,  Fig.  41,  which  was  first  manufactured  in  1876. 

FIG.  41. 


Being  of  small  dimensions,  of  compact  form,  and  yielding  an 
abundant  current,  it  was  well  adapted  to  the  wants  of  the  elec- 
tro-plater, and  hence  it  met  with  pronounced  success,  and  to  it 
can  be  traced  the  sudden  development  of  electro-plating  and 
electrotyping  in  this  country.  Many  of  these  machines  are  still 
in  use. 

An  iron  ring  or  cylinder  attached  to  an  iron  base  forms  the 
outer  shell  of  the  machine.     From  the  interior  of  this  cylinder, 


78  ELECTRO-DEPOSITION   OF   METALS. 

and  projecting  radially  towards  the  centre  of  the  apparatus, 
are  aranged  a  number  of  magnets  (usually  five),  which  consist 
of  a  core  of  iron  to  which  are  fastened  a  number  of  thin  tem- 
pered steel  plates,  and  they  are  wrapped  with  insulated  copper 
wire  and  so  connected  that  the  poles  shall  be  alternately  north 
and  south.  In  the  central  space  left  between  the  inward  ends 
of  these  magnets  is  arranged  a  shaft  carried  by  bearings,  which, 
to  secure  greater  strength  and  perfect  alignment,  are  cast  on  the 
iron  disks  or  heads  which  are  accurately  fitted  and  bolted  to  the 
ends  of  the  cylinder.  To  the  shaft  is  secured  a  series  of  arma- 
tures made  in  segments.  The  armatures  are  of  iron  and  also 
wrapped  with  wire.  When  revolved  the  outwardly  projecting 
ends  of  these  armatures  will  pass  closely  to,  but  without 
touching  the  inwardly  projecting  ends  of  the  magnets. 
The  commutator  is  made  in  two  pieces,  and  requires 
but  two  springs  to  carry  the  currents  from  all  the  arma- 
tures. These  springs  or  brushes  are  clamped  in  sockets  pro- 
jecting from  the  front  disk  of  the  cylinder.  An  automatic  switch 
or  governor  is  attached  to  this  machine  for  the  purpose  of  pre- 
venting it  from  reversing  by  the  polarization  of  the  electrodes. 

FIG.  42.  FIG.  43. 


In  1885,  the  ''Little  Wonder"  dynamo,  Fig.  42,  was  intro- 
duced, and  became  very  popular.  In  1886,  the  Hanson  &  Van 
Winkle  Co.  began  manufacturing  the  "Wonder"  dynamo,  Fig. 
43.  It  embodied  many  new  improvements  and  it  was  thought 


GALVANIC    ELEMENTS. 


79 


perfection  had  been  reached.  However,  in  1891,  electrical  sci- 
ence had  developed  so  many  entirely  new  features  that  the 
above  mentioned  firm  brought  out  their  H.  &  V.  W.  dynamo, 
shown  in  Fig.  44.  K  is  the  coil  of  the  field  magnet,  A  the  re- 
volving armature,  and  C  the  commutator,  BB  are  the  brushes 
for  picking  up  the  currents  of  electricity  produced  in  the  arma- 
ture by  revolving  in  the  magnetic  field  and  causing  them  to  flow 

FIG.  44. 


in  one  direction.  The  current  is  not  produced  by  friction.  D 
is  the  lever  to  adjust  the  position  of  the  brushes  to  the  commu- 
tator. NN  are  ^  inch  copper  rods  from  the  machine  to  the 
tank  or  to  the  main  conductors  on  the  wall.  The  binding-post 
on  the  machine  marked  P  is  joined  to  rods  connected  with  the 
anodes,  while  N  is  connected  to  the  object  rods.  The  rods  on 
the  tank  should  be  kept  bright  with  emery  paper.  When  but 
one  tank  is  used,  make  direct  connection  in  the  same  way  after 


So 


ELECTRO-DEPOSITION    OF    METALS. 


getting  the  speed  of  the  machine  satisfactory  for  the  maximum 
amount  of  work.  The  current  may  be  decreased  for  small  sur- 
iaces  by  moving  the  handle  of  the  resistance  board  from  the 
point  marked  "  strong,"  one  segment  at  a  time,  until  it  is  found 
to  answer.  The  position  of  the  brushes,  as  shown  in  the  cut, 
is  the  strongest  point.  By  moving  to  the  right  or  left  the  cur- 
rent is  diminished.  A  slight  change  of  position  of  the  brushes 
is  sometimes  an  advantage  in  setting  the  brushes  when  running 
on  large  surfaces,  to  avoid  sparks. 

In  using  the  resistance  boards,  (see  later  on)  they  are  put  up 

FIG.  45. 


as  near  the  tank  as  possible — the  weak  point  being  used  when 
putting  work  in  the  tank,  and  then  the  strength  of  current  is  in- 
creased until  the  power  required  is  obtained. 

The    proper   current   for   nickel-plating   on    brass  or  other 


GALVANIC    ELEMENTS. 


8l 


smooth  surfaces,  is  when  the  gas  is  seen  to  adhere  to  the  work, 
and  there  is  no  tendency  to  blacken  edges. 

The  new  H.  &  V.  W.  dynamo,  which  is  the  latest  improve- 
ment in  plating  dynamos  manufactured  by  the  Hanson  &  Van 
Winkle  Co.,  of  Newark,  N.  J.,  is  shown  in  Figs.  45,  46,  and  47. 


THE  HANSON  &  VAWW/NKLE   COMPANY. 

CA60  NEWARK.  N.J  Ntyv    TO" 


This  new  slow-speed,  iron-clad,  compound-wound  machine 
reaches  the  highest  degree  of  excellence.  The  distinctive 
feature  of  this  machine  is  the  construction  of  the  field  magnets 
and  of  the  frame,  which  are  cast  in  one  single  casting.  This 

FIG.  47. 


construction  gives  a  magnetic  field  of  much  greater  intensity 
than  can  otherwise  be  obtained,  and  entirely  prevents  all  waste- 
ful induced  currents  in  magnets  and  pole  pieces,  points  of  the 
greatest  importance  and  essential  to  high  efficiency. 

The  magnetic  circuit  is  of  unusually  low  resistance  by  reason 
6 


82  ELECTRO-DEPOSITION    OF   METALS. 

of  its  shape,  its  shortness  and  the  superior  quality  of  iron  used. 
There  is  no  magnetism  in  the  frame,  base  or  shaft,  as  the  mag- 
nets are  supported  at  some  distance  from  the  base  of  the 
machine.  There  is,  therefore,  no  opportunity  for  magnetic 
leakage,  and  besides  the  whole  is  enclosed  by  a  shield  or  case 
of  metal. 

The  regulation  of  the  voltage  is  entirely  automatic,  holding  a 
constant  voltage  from  no  load  to  the  full  capacity  of  the 
dynamo.  This  result  has  heretofore  been  accomplished  by  the 
use  of  resistance  rheostats,  etc.,  requiring  constant  attention,  in 
case  the  number  of  square  feet  of  surface  in  the  vats  is  varied, 
which  is  liable  to  burn  the  work  if  a  light  load  is  in  the  tanks. 
This  has  been  overcome  by  the  compound  windings.  A  saving 
in  the  consumption  of  power  required  is  also  made,  as  the 
machine  adjusts  itself  immediately  to  whatever  load  is  placed 
thereon,  from  a  single  piece  in  the  vats  or  to  the  full  load  of  the 
dynamo. 

The  armature  is  of  a  drum  type  and  is  built  up  of  thin  disks, 
all  of  which  are  securely  fastened  to  the  shaft.  The  winding  is 
a  modification  of  the  Siemens  method,  and  the  mode  of  con- 
necting and  collecting  the  current  from  the  same  produces  a 
current  as  steady  as  any  battery  could  give. 

The  armature  is  so  proportioned  that  it  has  but  little  idle  wire 
over  the  heads  and  is  only  wound  with  one  layer  of  wire.  The 
winding  is  done  with  the  greatest  care,  and  so  insulated  that 
there  is  little  danger  of  short  circuiting  and  burning  out.  The 
ends  of  the  armature  and  the  electrical  connections  are  thor- 
oughly covered,  thereby  protecting  them  from  copper  dust  or 
dirt  of  any  kind. 

The  necessary  voltage  is  secured  by  revolving  a  compara- 
tively small  number  of  coils  of  wire  in  a  powerful  magnetic  field, 
rather  than  by  using  a  large  number  of  coils  and  weak  field,  as  is 
the  usual  practice.  The  small  amount  of  wire  on  the  armature 
accounts  in  a  great  measure  for  the  absence  of  sparking  at  the 
brushes. 

The  commutator  is  insulated  with  mica,  and  is  of  ample  length 


GALVANIC    ELEMENTS.  83 

of  surface  to  secure  the  best  action  and  reduce  the  wear  to  a 
minimum. 

The  segments  are  pure  tempered  copper,  the  most  durable 
material  known  for  the  purpose,  and  when  necessary  may  be 
removed  without  returning  the  machine  to  the  factory.  The 
shaft  is  made  of  the  best  crucible  steel,  of  great  diameter  in  its 
central  part,  accurately  turned  and  finished  in  the  best  possible 
manner.  All  armatures  of  the  same  size  are  interchangeable. 

The  slow  speed  of  this  dynamo  is  a  most  important  point  for 
consideration,  it  being  run  at  about  half  the  speed  of  other 
makes  of  plating  machines  of  equal  cost. 

The  journals  are  of  generous  dimensions,  resting  in  bronze 
bearings  of  the  finest  quality.  They  are  self-aligning  and  self- 
oiling,  with  carrier  rings  in  each  bearing.  The  oil  wells  are  of 
ample  size  to  hold  enough  oil  for  two  or  three  months'  supply. 
In  this  manner  the  bearings  are  automatically  oiled  by  the 
motion  of  the  shaft,  and  they  require  no  attention  beyond  a 
periodical  examination  and  removal  of  oil. 

The  advantages  claimed  by  the  manufacturers  for  this 
dynamo  are  as  follows  :  i.  High  efficiency ;  therefore  economy 
of  power.  2.  Current  generated  without  any  sparking  at  the 
brushes ;  therefore  steady  current,  and  small  wear  of  brushes 
and  commutator.  3.  Solidity  of  construction  ;  therefore  safety 
against  interruptions  from  external  injury,  and  no  risk  in  trans- 
portation. 4.  Accessibility  of  the  different  parts  and  simplicity 
of  design.  5.  No  scattering  of  the  lines  of  force;  therefore  no 
external  magnetism  or  the  attraction  of  pieces  of  iron,  or  the 
magnetizing  of  watches  and  compasses,  etc.  6.  Perfect  regu- 
lation. 7.  Self-oiling  bearings.  8.  Ninety-five  per  cent,  effi- 
ciency. 9.  Slow  speed.  10.  Self-aligning  bearings,  n.  Me- 
chanical perfection.  12.  Work  equally  well  with  light  or  heavy 
load,  and  will  do  more  work  for  the  same  power  and  first  cost 
than  any  other  make  of  plating  machines  now  on  the  market. 

Detailed  descriptions  of  other  machines,  such  as  the  Miiller, 
Mather,  Elmore,  Biirgin,  Gulcher,  etc.,  would  needlessly 
lengthen  this  chapter.  The  great  impulse  which  the  art  of 


XJNlVEBSlTT 


84  ELECTRO-DEPOSITION    OF   METALS. 

electro-plating  has  in  modern  times  received  is  largely 
due  to  the  important  improvements  that  have  been  made 
in  the  construction  of  dynamo-electric  machines,  by  which 
mechanical  energy  generated  by  the  steam-engine  or  other 
convenient  source  of  power  may  be  directly  converted  into 
electrical  energy.  Without  dynamos  it  would  be  impossible  to 
electro-plate  large  parts  of  machines,  architectural  ornaments, 
etc.,  which  are  thus  protected  from  the  influence  of  the  weather. 
They  may  safely  be  credited  with  having  called  into  existence 
an  important  branch  of  the  electro-plating  art,  viz.,  nickel- 
plating,  and  especially  the  nickel-plating  of  zinc  sheets  as  well 
as  sheets  of  copper,  brass,  steel,  and  tin,  which  would  have  been 
impossible  if  the  manufacturer  had  to  rely  upon  the  generation 
of  the  electric  current  by  batteries.  The  latter,  at  the  very 
best,  are  troublesome  to  manage ;  they  only  give  out  their  full 
power  when  freshly  charged,  and  as  the  chemical  actions  upon 
which  they  rely  for  their  power  progress,  they  deteriorate  in 
strength  and  require  frequent  additions  of  acids  and  salts  to  be 
freshly  charged,  and  their  use  demands  constant  vigilance  and 
attention.  Even  when  working  on  a  small  scale,  it  is  cheapest 
to  procure  a  small  gas  or  other  motor  for  driving  a  small 
dynamo,  the  lathes,  and  grinding  and  polishing  machines. 

To  make  it  possible  for  the  manufacturer  of  dynamos  to 
suggest  the  most  suitable  machine,  the  following  data  should 
be  submitted  to  him:  — 

1.  Variety,  size,  and  number  of  the  baths  which   are  to  be 
fed  by  the  machine. 

2.  The  average  surface  of  the  articles  in  the  bath,  or  their 
maximum  surface,  and  the  metals  of  which  they  consist. 

3.  Whether  at  one  time  many  and  at  another  time  few  articles 
are  suspended  in  the  bath. 

4.  The  distance  at  which  the  machine  can  be  placed  from  the 
baths. 

5.  The  power  at  disposal. 


IV. 


PRACTICAL     PART. 



CHAPTER  IV. 

ARRANGEMENT   OF  ELECTRO- PLATING   ESTABLISHMENTS 
IN   GENERAL. 

ALTHOUGH  rules  valid  for  all  cases  cannot  be  given,  because 
modifications  will  be  necessary  according  to  the  size  and  extent 
of  the  establishment,  the  nature  of  the  articles  to  be  electro- 
plated, and  the  method  of  the  process  itself,  there  are,  never- 
theless, certain  main  features  which  must  be  taken  into  con- 
sideration in  arranging  every  establishment,  be  it  large  or  small. 
Only  rooms  with  sufficient  light  should  be  used,  since  the  eye 
of  the  operator  is  severely  taxed  in  judging  whether  the  articles 
have  been  thoroughly  freed  from  fat,  in  recognizing  the  differ- 
ent tones  of  color,  etc.  A  northern  exposure  is  especially 
suitable,  since  otherwise  the  reflection  caused  by  the  rays  of 
the  sun  may  exert  a  disturbing  influence.  For  large  establish- 
ments the  room  containing  the  baths  should,  besides  side-lights, 
be  provided  with  a  sky-light,  which,  according  to  the  location, 
is  to  be  protected  by  curtains  from  the  rays  of  the  sun. 

Due  consideration  must  be  given  to  the  frequent  renewal  of 
the  air  in  the  rooms.  Often  it  cannot  be  avoided  that  the 
operations  of  pickling,  etc.,  must  be  carried  on  in  the  same 
room  in  which  the  baths  are  located.  Especially  unfavorable 
in  this  respect  are  smaller  establishments  working  with  batteries, 
in  which  the  vapors  evolved  from  the  latter  are  added  to  the 
other  vapors,  and  render  the  atmosphere  injurious  to  health. 

(85) 


86  ELECTRO-DEPOSITION   OF   METALS. 

Hence,  if  possible,  rooms  should  be  selected  having  windows 
on  both  sides,  so  that  by  opening  them  the  air  can  at  any  time 
be  renewed,  or  the  baths  and  batteries  should  be  placed  in 
rooms  provided  with  chimneys ;  by  cutting  holes  of  sufficient 
size  in  the  chimneys  near  the  ceilings  of  the  rooms  the  discharge 
of  injurious  vapors  will  in  most  cases  be  satisfactorily  effected. 

To  those  working  with  Bunsen  elements,  it  is  recommended 
to  place  them  in  a  closet  varnished  with  asphalt  or  ebonite 
lacquer,  and  provided  with  lock  and  key.  The  upper  portion 
of  the  closet  should  communicate  by  means  of  a  tight  wooden 
flue  with  a  chimney  or  the  open  air. 

Since  the  baths  work  with  greater  difficulty,  slower  and  more 
irregular  below  a  certain  temperature,  provision  for  the  suffi- 
cient heating  of  the  operating  rooms  must  be  made.  Except 
baths  for  hot  gilding,  platinizing,  etc.,  the  average  temperature 
of  the  plating  solutions  should  be  from  64.5°  to  68°  F.,  at 
which  they  work  best;  it  should  never  be  below  59°  F.,  for 
reasons  to  be  explained  later  on.  Hence,  for  large  operating 
rooms  such  heating  arrangements  must  be  made  that  the  tem- 
perature of  the  baths  cannot  fall  below  the  minimum  even 
during  the  night,  otherwise  provision  for  the  ready  restoration 
of  the  normal  temperature  at  the  commencement  of  the  work 
in  the  morning  has  to  be  made.  Rooms  heated  during  the  day 
with  waste  steam  from  the  engine,  generally  so  keep  the  baths 
during  the  winter — the  only  season  of  the  year  under  consider- 
ation— that  they  show  in  the  evening  a  temperature  of  64.5°  to 
68°  F.,  and  if  the  room  is  not  too  much  exposed,  the  tempera- 
ture, especially  of  large  baths,  will  only  in  rare  cases  be  below 
59°  F.  For  greater  security  the  heating  pipes  may  be  placed 
in  the  neighborhood  of  the  baths ;  if  this  should  not  suffice  to 
protect  the  baths  from  cooling  off  too  much,  it  is  advisable  to 
locate  in  the  operating  room  a  steam  conduit  of  small  cross- 
section  fed  from  the  boiler  and  to  pass  steam  for  a  few  minutes 
through  a  coil  of  metal  indifferent  to  the  plating  solution  sus- 
pended in  the  bath.  In  this  manner  baths  of  1000  quarts, 
which,  on  account  of  several  days'  interruption  in  the  opera- 


ELECTRO-PLATING   ESTABLISHMENTS.  87 

tion,  had  cooled  to  36°  F.,  were  in  ten  minutes  heated  to 
68°  F.  For  smaller  baths  it  is  better  to  bring  a  small  por- 
tion of  them  in  a  suitable  vessel  to  the  boiling-point,  over  a  gas 
flame,  and  add  it  to  the  cold  bath,  and  if,  after  mixing,  the 
temperature  of  the  bath  is  still  too  low,  repeating  the  operation. 

Another  important  factor  for  the  operating  rooms  is  the  con- 
venient renewal  of  the  waters  required  for  rinsing  and  cleansing. 
Without  water  the  electro-deposition  of  metals  is  impossible ; 
the  success  of  the  process  depending  in  the  first  place  on  the 
careful  cleansing  of  the  metallic  articles  to  be  electro-plated, 
and  for  that  purpose  water,  nay,  much  water,  hot  and  cold,  is 
required,  as  will  be  seen  in  the  "  Preparation  of  the  Articles." 
Large  establishments  should,  therefore,  be  provided  with  pipes 
for  the  admission  and  discharge  of  water,  one  conduit  termina- 
ting as  a  rose  over  the  table  where  the  articles  are  freed  from 
grease.  In  smaller  establishments,  where  the  introduction  of  a 
system  of  water-pipes  would  be  too  expensive,  provision  must 
be  made  for  the  frequent  renewal  of  the  cleansing  water  in  the 
various  vats. 

In  consequence  of  rinsing  and  transporting  the  wet  articles 
to  the  baths  much  moisture  collects  upon  the  floor  of  the  oper- 
ating rooms.  The  best  material  for  floors  of  large  rooms  is 
asphalt,  it  being,  when  moist,  less  slippery  than  cement;  a 
pavement  of  brick  or  mosaic  laid  in  cement  is  also  suitable,  but 
has  the  disadvantage  of  cooling  very  much.  The  pavement  of 
asphalt  or  cement  should  have  a  slight  inclination,  a  collecting 
basin  being  located  at  the  lowest  point,  which  also  serves  for 
the  reception  of  the  rinsing  water.  Wood  floors  cannot  be 
recommended,  at  least  for  large  establishments,  since  the  con- 
stant moisture  causes  the  wood  to  rot ;  however,  where  their 
use  cannot  be  avoided,  the  places  where  water  is  most  likely  to 
collect  should  be  strewn  with  sand  or  saw-dust,  frequently  re- 
newed, or  the  articles  when  taken  from  the  rinsing  water  or 
bath  be  conveyed  to  the  next  operation  in  small  wooden 
buckets  or  other  suitable  vessels. 

The  operating  room  should  be  of  such  a  size  as  to  permit  the 


88  ELECTRO-DEPOSITION   OF   METALS. 

convenient  execution  of  the  necessary  manipulations.  Of 
course,  no  general  rule  can  be  laid  down  in  this  respect,  as  the 
size  of  the  room  required  depends  on  the  number  of  the  pro- 
cesses to  be  executed  in  it,  the  size  and  number  of  articles  to 
be  electro-plated  daily,  or  within  a  certain  time,  etc.  However, 
there  must  be  sufficient  room  for  the  batteries  or  dynamo,  for 
the  various  baths,  between  which  there  should  be  a  passage- 
way at  least  twenty  inches  wide,  for  the  table  where  the  arti- 
cles are  freed  from  grease,  for  the  lye  kettle,  hot-water  reser- 
voir, saw-dust  receptacle,  tables  for  tying  the  articles  to  hooks, 
etc. 

The  rooms  used  for  grinding,  polishing,  etc.,  also  require  a 
good  light  in  order  to  enable  the  grinder  to  see  whether  the 
article  is  ground  perfectly  clean,  and  all  the  scratches  from  the 
first  grinding  are  removed.  Where  iron  or  other  hard  metals 
are  ground  with  emery,  it  is  advisable  to  do  the  polishing  in  a 
room  separated  from  the  grinding  shop  by  a  close  board  parti- 
tion, because  in  the  preparatory  grinding  with  emory,  which  is 
done  dry,  without  the  use  of  oil  or  tallow,  the  air  is  impreg- 
nated with  fine  particles  of  emery,  which  settle  upon  the  polish- 
ing disks  and  materials,  and  in  polishing  soft  metals  cause  fine 
scratches  and  fissures  injurious  to  the  appearance  of  the  articles 
and  difficult  to  remove  by  polishing.  Hence,  all  operations  re- 
quiring the  use  of  emery,  or  coarse  grinding  powders,  should 
be  performed  in  the  actual  grinding- room,  as  well  as  the  grind- 
ing upon  stones  and  scratch-brushing  by  means  of  rapidly  re- 
volving steel  scratch-brushes.  Articles  already  electro-plated 
are,  of  course,  scratch- brushed  in  the  plating-room  itself,  either 
on  the  table  used  for  freeing  the  articles  from  grease,  or  on  a 
bench  especially  provided  for  the  purpose.  In  the  polishing 
room  are  only  placed  the  actual  polishing  machines,  which 
by  means  of  rapidly  revolving  disks  of  felt,  flannel,  etc.,  and 
the  use  of  -polishing  powders,  or  polishing  compositions,  im- 
part to  the  articles  the  final  lustre  before  and  after  electro-plat- 
ing. The  formation  of  dust  in  the  polishing  rooms  is  gener- 
ally over-estimated  ;  it  is,  however,  sufficiently  serious  to  render 


ELECTRO-PLATING   ESTABLISHMENTS.  89 

necessary  the  separation  by  a  close  partition  of  the  polishing 
rooms  from  the  electro-plating  room,  otherwise  the  polishing 
dust  might  settle  upon  the  baths  and  give  rise  to  various  dis- 
turbing phenomena.  In  rooms  in  which  large  surfaces  are 
polished  with  Vienna  lime,  as,  for  instance,  nickeled  sheets, 
the  dust  often  seriously  affects  the  health  of  the  polishers, 
especially  in  badly  ventilated  rooms,  and  in  such  cases  it  is 
advisable  to  provide  an  effective  ventilator.  If  this  cannot  be 
done,  wooden  frames  covered  with  packing-cloth,  placed  oppo- 
site the  polishing  disks,  render  good  service ;  the  packing- 
cloth,  by  being  frequently  moistened,  retaining  a  large  portion 
of  the  polishing  dust. 

For  grinding  lathes  requiring  the  belt  to  be  thrown  off  in 
order  to  change  the  grinding,  it  is  best  to  place  the  trans- 
mission carrying  the  belt-pulleys  at  a  distance  of  about  three 
feet  from  the  floor;  for  lathes  with  spindles  outside  the  bearings 
the  transmission  may  be  on  the  ceiling  or  wall.  The  revolving 
direction  of  the  principal  transmission  should  be  such  as  to 
render  the  crossing  of  the  belts  to  the  grinding  and  polishing 
machines  unnecessary,  otherwise  the  belts  on  account  of  the 
great  speed  will  rapidly  wear  out. 

ELECTRO-PLATING  ARRANGEMENTS  IN  PARTICULAR. 

The  actual  electro-plating  plant  consists  of  the  following  parts  : 
i.  The  sources  of  current  (batteries  or  dynamo-electric  ma- 
chines) with  auxiliary  apparatus.  2.  The  current-conductors. 

3.  The  baths,  consisting  of  the  vats,  the  plating  solution,  the 
anodes,   and   the   conducting   rods   with  their  binding-screws. 

4.  The  apparatuses    for  cleansing,   rinsing,  and    drying.     The 
sources  of  current  have  already  been  discussed  in  Chapter  III. 
p.  32,  and  the  laws  governing  the  suitable  coupling  cf  the  ele- 
ments on  p.  19. 

A.  Arrangement  with  elements. — In  working  with  elements  it 
is  first  necessary  to  have  a  clear  idea  of  the  area  of  the  articles 
which  are  to  be  at  one  time  electro-plated  in  a  bath,  and  of  the 
magnitude  of  the  resistance  opposed  by  the  bath  to  the  current. 


go  ELECTRO-DEPOSITION   OF   METALS. 

This  and  the  size  of  the  anodes  show  how  many  elements  must 
be  put  together  for  a  battery,  and  how  the  elements  are  to  be 
coupled.  Suppose  we  have  a  nickel  bath  which  requires  for 
its  decomposition  a  current  of  2.5  volts  of  electro-motive  force 
or  tension ;  now  since,  according  to  p.  40,  a  Bunsen  element 
yields  a  current  of  1.88  volts,  the  reduction  of  the  nickel  can- 
not be  effected  with  one  such  element,  but  two  elements  must 
be  coupled  for  tension  one  after  the  other,  whereby,  leaving 
the  conducting  resistance  of  the  wires  out  of  consideration,  an 
electro-motive  force  or  tenson  of  2x1.88=3.76  volts  is  ob- 
tained, with  which  the  decomposition  of  the  solution  can  be 
effected.  If,  on  the  other  hand,  we  have  a  silver  bath  which 
requires  only  y2  volt  for  its  decomposition,  we  do  not  couple 
two  elements  one  after  the  other,  because  the  electro-motive 
force  of  a  single  element  suffices  for  the  reduction  of  the  silver 
On  p.  19  it  has  been  seen  that  by  coupling  the  elements  one 
after  the  other  (coupling  for  tension)  the  electro-motive  force  of 
the  battery  is  increased,  but  the  quantity  of  current  is  not  in- 
creased, and  that  to  attain  the  latter  the  elements  must  be 
coupled  alongside  of  one  another  (coupled  for  quantity). 
Hence  in  a  group  of,  for  instance,  three  elements  coupled  one 
after  another,  only  one  single  zinc  surface  of  the  elements  can 
be  considered  effective  in  regard  to  the  quantity  of  current. 
Now,  the  larger  the  area  of  articles  at  the  same  time  suspended 
in  the  bath  is,  the  greater  the  number  of  such  effective  zinc 
surfaces  of  the  group  of  elements  to  be  brought  into  action 
must  be,  and,  if  for  baths  with  medium  resistance,  it  may  be 
laid  down  as  a  rule  that  the  effective  zinc  surface  must  be  at 
least  as  large  as  the  area  of  the  articles ;  provided  the  surface  of 
the  anodes  is  at  least  equal  to  the  latter,  the  approximate  num- 
ber of  elements  and  their  coupling  for  a  bath  can  be  readily 
found.  Let  us  take  the  nickel  bath,  which,  as  above  mentioned, 
requires  a  current  of  2.5  volts,  and  for  the  decomposition  of 
which  two  elemenfs  must,  therefore,  be  coupled  one  after  the 
other,  and  suppose  that  the  zinc  surface  of  the  Bunsen  elements 
is  500  square  centimetres,  then  the  effective  zinc  surface  of  the 


ELECTRO-PLATING   ESTABLISHMENTS.  9 1 

two  elements  coupled  one  after  the  other  will  also  be  500 
square  centimetres;  hence  a  brass  sheet  20x25  =  500  centi- 
metres can  be  conveniently  nickeled  on  one  side  with  these 
two  elements,  or  a  sheet  10x25  =  250  centimetres  on  both  sides. 
Now  suppose  the  surface  to  be  nickeled  were  twice  as  large, 


FIG.  48. 


then  the  two  elements  would  not  suffice,  and  a  second  group 
of  two  elements,  coupled  one  after  the  other,  would  have  to  be 
joined  to  the  first  group  for  quantity  as  shown  in  Fig.  4,  or 
perspectively  in  Fig.  48.  Three  times  the  object  surface  would 
require  three  groups  of  elements,  and  so  on. 

However,  this,  to  a  certain  extent,  empirical  determination  of 
the  number  of  elements  required  for  plating  surfaces  of  definite 
measure  may  be  abandoned,  and  we  may  avail  ourselves  of  a 
more  exact  determination  according  to  electrical  values,  since 
at  the  present  time  the  electrical  relations  of  the  baths  are 
accurately  known  and  the  performances  of  the  elements  as  well 
as  of  the  dynamos  are  specified  according  to  current  quantity 
and  current  tension. 

As  regards  the  result  of  the  process  of  deposition,  the  first 
requisite  which  has  to  be  taken  into  account  is  that  a  sufficient 
quantity  of  current  acts  upon,  the  surface  to  be  plated,  and  the 
next  that  the  current  possesses  the  necessary  tension  for  the 
decomposition  of  the  bath.  ,  Now  the  current  quantity  which 
is  required  for  the  correct  formation  of  the  deposit  upon  I 


92  ELECTRO-DEPOSITION    OF   METALS. 

square  decimeter  *  =10x10  centimeters  f  ( 100  square  centi- 
meters) may  be  designated  as  the  current-density,  and  in  the 
plating  processes  described  later  on,  the  suitable  current-density 
is  always  given.  If  now,  for  instance,  this  current-density  for  a 
nickel  bath  is  O.6  ampere  per  sq.  dcm.,  the  tension  2.5  volts 
and  the  largest  surface  to  be  plated  in  the  bath  50  cm.X2O  cm. 
=  1000  sq.  cm.  or  10  sq.  dcm.  a  current-strength  of  at  least 
0.6X10=6  amperes  would  be  required.  Hence,  a  medium- 
large  element  furnishing  8  amperes  would  suffice  if  the  tension 
necessary  for  the  decomposition  of  the  electrolyte  did  not 
amount  to  2.5  volts.  As  previously  stated,  a  Bunsen  element 
furnishes  about  1.8  volts,  and  hence,  in  order  to  obtain  the 
higher  tension,  two  elements  must  be  coupled  one  after  the 
other,  and  the  excess,  which  would  be  an  impediment  to  the 
correct  formation  of  the  deposit,  has  to  be  destroyed  by  the 
current-regulator  to  be  described  later  on,  in  case  it  is  not  pre- 
ferred to  increase  the  object-surface. 

For  silvering,  the  current-density  amounts  to  0.25  ampere, 
and,  with  a  slight  excess  of  potassium  cyanide,  the  silver  bath 
requires  I  volt.  If  now,  for  instance,  an  object  surface  of  55 
sq.  dcm.,  which  is  about  equal  to  50  large  soup-spoons,  is  to  be 
silvered,  55x0.25=13.75  amperes  and  I  volt  are  required. 
Hence,  two  elements  of  8  amperes  each  must  be  coupled  along- 
side one  another  in  order  to  obtain  16  amperes  current-quantity, 
and  the  excess  destroyed  by  the  current-regulator. 

In  giving  these  illustrations  it  is  supposed  the  objects  are  to 
have  a  thick  solid  plating ;  for  rapid  plating  with  a  thin  deposit 
a  different  course  has  to  be  followed.  Only  a  slight  excess  of 
electro-motive  force  in  proportion  to  the  resistance  of  the  bath 
being  in  the  above-mentioned  case  present,  reduction  takes  place 
slowly  and  uniformly  without  violent  evolution  of  gas  on  the 
objects,  and  by  the  process  thus  conducted  the  deposit  formed 
is  sure  to  be  homogeneous  and  dense,  since  it  absorbs  but  slight 

*  i  square  decimeter  (sq.  dem.)  =15.501  square  inches. 
t  i  centimeter  (cm.)  =0.394  inch. 


ELECTRO-PLATING   ESTABLISHMENTS.  93 

quantities  of  hydrogen,  and  in  mosf  cases  it  can  be  obtained  of 
sufficient  thickness  to  be  thoroughly  resistant.  If,  however,  the 
operation  is  to  be  executed  quickly  and  without  regard  to  great 
solidity  and  thickness  of  the  deposit,  the  elements  have  to  be 
coupled  so  that  the  electro-motive  force  is  sufficiently  large  for 
the  current  to  readily  overcome  the  resistance  of  the  bath.  This 
is  attained  by  coupling  three,  four,  or  more  elements  one  after 
the  other,  as  shown  in  the  scheme  Fig.  2.  However,  such  de- 
posits can  never  be  homogeneous,  because  they  condense  and 
retain  relatively  large  quantities  of  hydrogen. 

As  regards  the  filling  and  other  management  of  the  batteries, 
the  reader  is  referred  to  pp.  37-43,  under  Bunsen  elements. 
Having  seen  how  many  elements  are  required,  and  how  they 
have  to  be  coupled  to  form  a  battery  for  certain  purposes,  we 
will  next  consider  the  auxiliary  apparatuses. 

Only  in  very  rare  cases  will  it  be  possible  to  always  charge  a 
bath  or  several  baths  with  the  same  object-area;  and  according 
to  the  amount  of  business,  or  the  preparation  of  the  objects  by 
grinding,  polishing,  and  pickling,  at  one  time  large,  and  at 
another  small,  areas  will  be  suspended  in  the  bath.  Now,  sup- 
pose a  battery  suitable  for  a  correct  deposit  upon  an  area  of,  say 
five  square  feet,  has  been  grouped  together;  and,  after  empty- 
ing the  bath,  a  charge  only  half  as  large  is  introduced,  the  cur- 
rent of  the  battery  will,  of  course,  be  too  strong  for  this  reduced 
area,  and  there  will  be  danger  of  the  deposit  not  being  homo- 
geneous and  dense,  but  forming  with  a  crystalline  structure,  the 
consequence  of  which,  in  most  cases,  will  be  slight  adhesive- 
ness, if  not  absolute  uselessness.  With  sufficient  attention  the 
total  spoiling  of  the  articles  might  be  prevented  by  removing 
the  objects  more  quickly  from  the  bath.  But  this  is  groping  in 
the  dark,  the  objects  being  either  taken  too  soon  from  the  bath, 
when  not  sufficiently  plated,  or  too  late,  when  the  deposit  al- 
ready shows  the  conseqences  of  too  strong  a  current. 

To  control  the  current  an  instrument  called  the  rheostat,  cur- 
rent-regulator, resistance  board,  or  switch  board,  has  been  con- 
ducted, which  allows  of  the  current-strength  ,of  a  battery  being 


94 


ELECTRO-DEPOSITION   OF   METALS. 


reduced  without  the  necessity  of  uncoupling  elements.  It  is 
evident  that  the  current  of  a  battery,  if  too  strong,  can  be 
weakened  by  decreasing  the  number  of  elements  forming  the 
battery,  and  also  by  decreasing  the  surface  of  the  anodes,  be- 
cause the  external  resistance  is  thereby  increased.  This  coup- 
ling and  uncoupling  of  elements  is,  however,  not  only  a  time- 
consuming,  but  also  a  disagreeable  labor;  and  it  is  best  to  use 
a  resistance  board,  with  which  by  the  turn  of  a  handle,  the 
desired  end  is  attained.  Figs.  49  and  50  show  this  instrument. 

Fig.  49. 


To  the  Bath 


TotheBqtfu 


Its  action  is  based  upon  the  following  conditions :  As  ex- 
plained on  p.  21,  the  maximum  performance  of  a  battery  takes 
place  when  the  external  resistance  is  equal  to  the  internal  re- 
sistance of  the  battery.  By  increasing  the  external  resistance, 
the  performance  is  decreased,  and  a  current  of  less  intensity 
will  pass  into  the  bath  when  resistances  are  placed  in  the 
circuit.  The  longer  and  thinner  the  conducting  wire  is,  and 
the  less  conducting  power  it  possesses,  the  greater  will  be  the 
resistance  which  it  opposes  to  the  current.  Hence,  the  re- 
sistance board  consists  of  metallic  spirals  which  lengthen  the 
circuit,  contract  it  by  a  smaller  cross-section,  and  by  the  nature 
of  the  metallic  wire  have  a  resistance-producing  effect.  For  a 
slight  reduction  of  the  current,  copper  spirals  of  various  cross- 


;     ' 


ELECTRO-PLATING   ESTABLISHMENTS.  95 

sections  are  taken,  which  are  succeeded  by  brass  spirals,  and 
finally  by  German  silver  spirals,  whose  resistance  is  eleven 
times  greater  than  that  of  copper  spirals  of  the  same  length 
and  cross-section.  In  Fig,  49  the  conducting  wire  coming 
from  the  battery  goes  to  the  screw  on  the  left  side  of  the 
resistance  board,  which  is  connected  by  stout  copper  wire  with 
the  first  contact-button  on  the  left;  hence  by  placing  the 
metallic  handle  upon  the  button  furthest  to  the  left,  the  current 
passes  the  handle  without  being  reduced,  and  flows  off  through 
the  conducting  wire  secured  in  the  setting-screw  of  the  handle. 
By  placing  the  handle  upon  the  next  contact-button  to  the 
right,  two  copper  spirals  are  brought  into  the  circuit;  by  turn- 
ing the  handle  to  the  next  button,  four  spirals  are  brought  into 
the  circuit,  and  so  on.  By  a  choice  of  the  cross-sections  of 
the  spirals,  their  length  and  the  metal  of  which  they  are  made, 
the  current  may  be  more  or  less  reduced  as  desired. 

To  control  the  reduction  of  the  current  effected  by  the  resist- 
ance, a  galvanometer  is  placed  behind  it.  It  consists  of  a  mag- 
netic needle  oscillating  upon  a  pin,  below  which  the  curren  ist 
conducted  through  a  strip  of  copper,  or,  with  weaker  currents, 
through  several  coils  of  wire.  The  electric  current  deflects  the 
magnetic  needle  from  its  position,  and  the  more  so  the  stronger 
the  current  is;  hence  the  current-strength  of  the  battery  can  be 
determined  by  the  greater  or  smaller  deflection. 

For  a  weak  current,  such  as,  for  instance,  that  yielded  by  two 
elements,  it  is  of  advantage  to   use   a  horizontal  galvanometer 
(Fig.   51).     It   is  screwed  to   a  table   by 
means  of  a  few  brass  screws  in  such  a  po-  FIG.  51- 

sition  that  the  needle  in  the  north  position, 
which  it  occupies,  points  to  o°  wrhen  no 
current  passes  through  the  instrument. 
Articles  of  iron  and' steel  must,  of  course, 
be  kept  away  from  the  instrument.  For 

stronger  currents,  it  is  better  to  combine  a  vertical  galvanometer 
with  the  resistance  board  and  fasten  it  to  the  same  frame,  as 
shown  in  Fig.  50.  The  screw  of  the  handle  of  the  resistance 


96 


ELECTRO-DEPOSITION    OF   METALS. 


board  is  connected  with  one  end  of  the  copper  strip  of  the  ver- 
tical galvanometer,  while  the  other  is  connected  with  the  screw 
on  the  right  side  of  the  resistance  board  in  which  is  secured  the 
wire  leading  to  the  bath.  The  resistance  board  and  galvano- 
meter are  placed  in  one  conducting  wire  oniy,  either  in  that  of 
the  anodes  or  of  the  objects ;  one  of  these  wires  is  simply  cut, 
and  the  end  connected  to  the  battery  is  secured  in  the  setting- 
screw  on  the  side  of  the  resistance  board  marked  "  strong," 
while  the  other  end  which  is  in  connection  with  the  bath  is  se- 
cured in  the  setting-screw  on  the  opposite  side  marked  "  weak." 
The  entire  arrangement  will  be  perfectly  understood  from  Figs. 
52  and  54. 

FIG.  52. 


Fig.  53  shows  an  improved  switchboard  or  rheostat,  which 
has  twice  the  carrying  power  of  other  resistance  boards  for  this 
purpose,  it  having  sufficient  length  of  wire  to  allow  of  toning 
down  the  highest  electro-motive  force  used  in  plating,  to  the 
lowest  figure  called  for,  without  showing  heat  or  any  unfavor- 
able symptoms.  By  the  use  of  this  switchboard  the  output 
from  a  plating  room  using  two  or  more  tanks  can  be  doubled, 
provided  the  dynamo  has  the  current  capacity. 


ELECTRO-PLATING   ESTABLISHMENTS.  9/ 

All  platers  understand  that  different  voltages  are  required  to 
operate  successfully  different  kinds  of  solutions,  and  that  when 
a  sufficient  voltage  is  to  be  generated  for  a  solution  of  the 
highest  resistance,  and  at  the  same  time  utilized  in  low  resist- 
ance solutions,  the  tank  nearest  the  dynamo,  with  the  ordinary 
method,  receives  the  most  current,  and  a  tendency  to  burn  and 
blacken  is  noticed  to  a  marked  de- 
gree. When  metals  such  as  silver 
and  copper  are  to  be  deposited  in 
connection  with  such  metals  as 
nickel  and  brass,  a  higher  electro- 
motive force  is  required,  and  a  con- 
siderable drop  in  voltage  is  de- 
manded in  the  lower  resistance 
solution  so  as  not  to  blacken  the 
work.  With  the  old  style  switch- 
boards this  is  done  at  a  great  loss 

of  current  and  work  capacity  of  tank.  With  the  old  style  switch- 
boards about  the  greatest  carrying  capacity  that  they  will  feed 
is  from  25  to  35  amperes,  not  over  35  amperes.  This  deficiency 
is  due  to  the  smallness  of  the  resistance  wire  and  lack  of  suffi- 
cient metal  conductivity.  With  the  improved  switchboard 
three  times  the  current  can  be  conveyed  without  showing  the 
least  heat  in  either  the  resistance  wires,  segments,  switch  or 
base- plate. 

Having  discussed  the  advantages  derived  from  the  use  of  the 
resistance  board,  it  remains  to  add  a  few  words  regarding  the 
indications  made  by  the  galvanometer.  Since  the  greater  de- 
flection of  the  needle  depends,  on  the  one  hand,  on  the  greater 
current-strength,  and,  on  the  other,  on  the  slighter  resistance 
of  the  outer  closing  arc  (conducting  wires,  baths,  and  anodes), 
it  is  evident  that  a  bath  with  slighter  resistance,  when  worked 
with  the  same  battery  and  containing  the  same  area  of  anodes 
and  objects,  will  cause  the  needle  to  deflect  more  than  a  bath 
of  greater  resistance  under  otherwise  equal  conditions.  Hence 
the  deductions  drawn  from  the  position  of  the  needle  for  the 
7 


98 


ELECTRO-DEPOSITION   OF   METALS. 


electro-plating  process  are  valid  only  for  determined  baths  and 
determined  equal  conditions,  but  with  due  consideration  of 
these  conditions  are  of  great  value.  Suppose  a  nickel  bath 
always  works  with  the  same  area  of  objects  and  of  anodes,  and 

FIG.  54. 


experiments  have  shown  that  the  suitable  current-strength  for 
nickeling  this  area  of  objects  is  that  at  which  the  needle  stands 
at  15°;  and  suppose  further  that  the  battery  has  been  freshly 
filled  and  causes  the  needle  to  deflect  to  25°,  then  the  handle 
of  the  resistance  board  will  have  to  be  turned  so  far  to  the  right 
that  the  needle,  in  consequence  of  the  introduced  resistances, 
returns  to  15°.  Now  if,  after  working  for  some  time,  the 
battery  yields  a  weaker  current,  the  needle,  since  the  resistance 
remains  the  same,  will  constantly  retrograde,  and  has  to  be 
brought  back  to  15°  by  turning  the  handle  to  the  left,  when  a 
current  of  equal  strength  of  the  former  will  again  flow  into  the 
bath.  This  play  is  repeated  until  finally  the  handle  stands 
upon  the  button  furthest  to  the  left,  at  which  position  the 
current  flows  directly  into  the  bath  without  being  influenced  by 
the  resistances  of  the  resistance  board.  If  now  the  needle 
retrogrades  below  15°,  it  is  an  indication  to  the  operator  that 


ELECTRO-PLATING   ESTABLISHMENTS.  99 

he  must  renew  the  filling  of  the  battery  if  he  does  not  prefer 
suspending  fewer  objects  in  the  bath.  For  this  reduced  object^ 
area  it  is  no  longer  required  for  the  needle  to  stand  at  15°  in 
order  to  warrant  a  correct  progress  of  the  galvanic  process, 
since  the  resistance  being  in  this  case  greater,  a  deflection  to 
10°,  or  still  less,  may  suffice.  This  illustration  will  sufficiently 
show  that  the  current-indication  by  the  galvanometer  is  not  and 
cannot  be  absolute,  but  that  the  deductions  must  always  be 
drawn  with  due  consideration  to  the  conditions — area  of  objects 
and  of  anodes,  and  distance  between  them.  An  operator  to  be 
sure  in  this  respect,  and,  above  all,  wishing  to  work  scien- 
tifically, will  replace  the  galvanometer  by  a  voltmeter,  which 
indicates  the  absolute  magnitude  of  the  electro-motive  force 
passing  into  the  bath,  as  will  be  explained  later  on. 

It  frequently  happens  that  in  consequence  of  defective  con- 
tacts with  the  binding-screws  of  the  battery,  or  by  the 
conductors  of  the  objects  and.  of  the  anodes  touching  one 
another  (short  circuit  with  non-insulated  conducting  wires), 
no  current  whatever  flows  into  the  bath.  Such  an  occurrence 
is  immediately  indicated  by  the  galvanometer,  the  needle  be- 
ing not  at  all  deflected  in  the  first  case,  while  in  the  latter  the 
deflection  will  be  entirely  different  from  the  usual  one.  The 
magnetic  needle  of  the  galvanometer  also  furnishes  a  means  of 
recognizing  the  polarity  of  the  current.  If  the  galvanometer 
be  placed  in  the  positive  conductor  by  securing  the  wire  com- 
ing from  the  battery  in  the  binding-screw  on  the  south  pole  of 
the  galvanometer,  and  the  wire  leading  to  the  bath  in  the  bind- 
ing-screw on  the  north  pole  of  the  needle,  the  needle,  accord- 
ing to  Ampere's  law,  will  be  deflected  in  the  direction  of  the 
hands  of  a  watch,  i.  e.,  to  the  right  if  the  observer  stands  so  in 
front  of  the  galvanometer  as  to  look  from  the  south  pole 
towards  the  north  pole,  because  the  battery  current  flows  out 
from  the  positive  pole  through  the  conducting  wire,  anodes, 
and  fluid  to  the  objects,  and  from  these  back  through  the 
object  wire  to  the  negative  pole  of  the  battery.  If  now  in  con- 
sequence of  the  counter- current  formed  in  the  bath  by  the 


IOO  ELECTRO-DEPOSITION   OF   METALS. 

metallic  surfaces  of  dissimilar  nature  (see  later  on),  and  flow- 
ing in  an  opposite  direction  to  that  of  the  battery-current,  the 
latter  is  weakened,  the  needle  will  constantly  further  retrograde 
from  the  zero  point,  and  when  the  counter  or  polarizing  cur- 
rent becomes  stronger  than  the  battery-current,  it  will  be 
deflected  in  an  opposite  direction  as  before.  Hence,  by 
observing  the  galvanometer  the  operator  can  avoid  the  annoy- 
ing consequences  of  polarization,  which  will  be  further  dis- 
cussed under  nickeling. 

The  observing  practical  electro-plater  will  know  that  the 
character  of  a  deposit  obtained  in  a  certain  solution  with  a  defi- 
nite area  of  objects  to  be  plated  depends  largely  upon  the  re- 
production of  certain  conditions,  and  especially  upon  the  density 
of  the  current  for  the  certain  area  to  be  plated.  To  reproduce 
such  conditions  it  is  highly  important  that  either  the  electro- 
motive force  existing  between  anode  and  cathode,  or  the  current 
flowing  through  the  same,  be  accurately  measured.  The  ordinary 
galvanometer  is  insufficient  and  often  misleading,  and  not  at  all 
satisfactory  for  the  actual  measurement  of  either  the  voltage  or 
current.  It  indicates  only  a  change  of  polarity,  a  cause  of 
trouble  not  often  accurring  with  the  use  of  a  good  dynamo.  If 
it  is  desired  to  measure  the  actual  E.  M.  F.  existing  at  the  ter- 
minal of  the  dynamo  or  bath,  only  the  very  best  voltmeters  or 
ammeters  should  be  used.  They  should  be  so  constructed  as 
to  indicate  quickly  and  accurately  any  sudden  changes  in  current, 
and  should  be  direct  reading  in  volts  and  amperes,  and  their 
indications  should  not  be  subjected  to  gradual  changes.  A 
sensitive  voltmeter  such  as  the  Weston  voltmeter  shown  in  Fig. 
55,  will  indicate  the  slipping  of  belts,  short  circuiting  in  tanks 
and  any  irregularities  in  power.  These  voltmeters  have  a  scale 
from  o  to  6  volts  and  upwards.  The  scale  is  divided  into  120 
divisions  so  that  each  division  represents  yf^  of  a  volt  and  when 
used  in  cannection  with  the  switch  board,  Fig.  54,  will  enable 
the  plater  to  study  carefully  all  the  requirements  that  insure 
good  results,  and  will  give  him  the  means  of  accurately  repro- 
ducing such  conditions  as  he  has  found  by  experience  con- 


ELECTRO-PLATING   ESTABLISHMENTS. 


101 


ducive  to  success.  One  voltmeter  can  be  made  to  answer  for  a 
number  of  tanks  by  means  of  a  shunt  from  which  the  wires  run 
to  each  tank.  By  this  arrangement,  and  in  connection  with  the 

FIG.  55. 


Switch-boards,  the  voltage  for  each  tank  and  the  current  passing 
through  the  tank  are  controlled. 

Whilst  it  will  be  sufficient  in  most  cases  to  use  a  voltmeter 
in  combination  with  a  rheostat  for  regulating  purposes,  it  will 
sometimes  be  found  desirable  to  determine  the  actual  amount 
of  current  in  amperes  passing  through  a  tank.  It  is  a  funda- 
mental law  of  electrolysis  that  a  certain  number  of  amperes 
passing  through  a  plating  solution  will  cause  a  definite  weight 
of  metal  to  be  deposited.  So,  for  instance,  one  ampere  will 


102 


ELECTRO-DEPOSITION    OF   METALS. 


deposit  in  one  hour  1.106  grammes  of  nickel,  or  4.05  grammes 
of  silver.  It  is  evident,  therefore,  that  by  means  of  an  accurate 
ammeter,  the  amount  of  metal  actually  deposited  can  easily  be 
determined.  The  Weston  ammeter,  shown  in  Fig.  56,  is  very 
sensitive,  indicating  the  slightest  variation  of  current  accurately 

FIG.  56. 


and  with  absolute  certainty.  It  is,  especially  for  higher  ranges, 
the  best,  the  most  economical,  and  at  the  same  time  the 
cheapest  instrument  in  the  market.  Both  the  Weston  volt- 
meter and  the  Weston  ammeter  are  furnished  by  Hanson  & 
Van  Winkle  Co.,  Newark,  N.  J. 

From  what  has  been  said  in  this  chapter  and  in  the  theoret- 
ical part,  it  is  self-evident  what  rules  have  to  be  observed  in 
conducting  the  current.  Since  the  current-strength  is  weak- 


ELECTRO -PLATING   ESTABLISHMENTS.  103 

ened  by  resistance,  the  cross-section  of  the  current-carrying 
wire  as  well  as  of  that  leading  to  the  objects  and  to  the  anodes 
must  be  of  a  size  corresponding  to  the  current-strength,  and 
the  material  for  the  wires  should  possess  as  high  a  conducting 
power  as  possible.  Chemically  pure  copper  is  best  suited  for 
this  purpose.  Some  information  for  calculating  the  thickness 
of  the  wires  will  be  found  at  the  end  of  the  section  "  Arrange- 
ment with  Dynamo  Machines." 

The  positive  or  anode  wire  effects  the  connection  between  the 
anodes  of  the  bath  and  the  positive  pole  (anode  or  carbon 
pole)  of  the  battery,  while  the  negative  or  object  wire  brings 
the  objects  in  the  bath  into  metallic  contact  with  the  negative 
(zinc)  pole  of  the  battery.  As  previously  mentioned,  the  re- 
sistance board  with  galvanometer  is  placed  in  one  or  the  other 
of  the  wires. 

For  conducting  the  electric  current  to  the  baths,  metallic 
wires,  bands,  spirals,  or  ribbons  are  used.  The  conducting 
wires  are  either  employed  in  their  natural  metallic  state,  or  are 
covered  with  some  insulating  or  poorly  conducting  substance, 
such  as  cotton,  silk,  India-rubber,  gutta-percha,  and  various 
varnishes.  It  is  evident  that  covered  wires  should  be  bare  and 
clean  at  their  extremities  where  they  are  connected  with  the 
battery  and  with  the  anodes  and  objects  to  be  plated.  Wires 
of  pure,  well-annealed  copper  possess  the  best  conducting 
power,  and  should  have  a  sectional  area  capable  of  carrying 
the  maximum  quantity  of  current  without  offering  appreciable 
resistance.  Cables  should  be  chosen  where  a  large  volume  of 
current  must  be  carried,  they  being  more  flexible  than  wire  of 
a  large  size,  and  can  be  more  easily  laid. 

Insulated  wires  may  come  in  contact  with  each  other  with- 
out inconvenience.  Such,  however,  is  not  the  case  with  bare 
wires ;  because  the  electricity  will  pass  through  the  shortest 
circuit  and  will  not  go  through  the  bath  if  the  two  wires  are  in 
metallic  contact.  Such  contact  should,  therefore,  be  carefully 
avoided. 

Vats  or  tanks. — These  are  the  vessels  to   hold  the  plating 


104 


ELECTRO-DEPOSITION    OF   METALS. 


solutions.  Their  shape  may  be  either  circular,  square,  or 
rectangular.  They  should  be  perfectly  tight,  impervious  to 
the  solutions,  and  unacted  upon  by  them.  They  are  made  of 
different  materials — stoneware,  glass,  or  porcelain  vats  being 
best,  but  they  are  the  most  fragile  and  expensive. 

Wooden  vats  must  be  carefully  constructed,  and  are  best 
secured  at  the  ends  by  bolts  and  nuts,  as  shown  in  Fig.  57, 
which  serve  to  hold  the  sides  firmly  against  the  end  pieces. 

FIG.  57. 


The  vat  is  then  coated  with  a  mixture  of  equal  parts  of  pitch 
and  rosin  boiled  with  a  small  quantity  of  linseed  oil.  Another 
mixture,  which  has  been  found  to  afford  a  good  protective 
covering  to  wood,  consists  of  10  parts  of  gutta-percha,  3  of 
pitch,  and  I  ^  each  of  stearin  and  linseed  oil,  melted  together 
and  incorporated. 

For  large  acid  copper  and  nickel  baths  wooden  vats  lined 
with  chemically  pure  sheet-lead  about  0.118  inch  thick,  and 
the  seams  soldered  with  pure  lead,  are  very  suitable.  Care 
must,  of  course,  be  taken  that  neither  the  conducting  rods  nor 
the  articles  suspended  in  the  bath  and  the  anodes  come  in  con- 
tact with  the  lead  lining,  which  with  some  care  can  be  readily 
avoided.  Objections  have  frequently  been  made  to  such  vats, 
but  in  Dr.  George  Langbein's  establishment  they  have  for  six 


ELECTRO-PLATING  ESTABLISHMENTS.  1 05 

years  been  used  for  nickel  baths  without  the  lead  having  the 
slightest  effect  upon  the  baths,  and  no  disturbance  in  the  work- 
ing of  the  latter  has  ever  been  observed.  After  careful  investi- 
gation such  lead -lined  vats  have  even  been  used  for  large 
copper  and  brass  baths  containing  potassium  cyanide  without 
the  slightest  injury  to  the  baths.  If  even  a  film  of  lead  cyanide 
is  formed  upon  the  lead,  it  is  insoluble  in  excess  of  potassium 
cyanide,  and  hence  is  entirely  indifferent  as  regards  the  bath. 
Only  for  nickel  baths  containing  large  quantities  of  acetates, 
citrates  and  tartrates  these  lead-lined  vats  cannot  be  recom- 
mended, since  these  salts  possess  a  certain  power  of  dissolving 
lead  oxide.  However,  the  use  of  such  baths  has  been  almost 
entirely  abandoned,  and  the  small  quantities  of  organic  acid 
which  occasionally  serve  for  correcting  the  reaction  of  a  nickel 
bath  need  not  be  taken  into  consideration.  The  lead-lining 
might  be  dispensed  with  if  it  were  not  for  the  difficulty  of  keeping 
wooden  vats  tight.  Many  plating  solutions  impair  the  swelling 
power  of  the  wood,  and  with  even  a  slight  change  in  the  tem- 
perature the  vats  become  pervious,  the  evil  increasing  in  time. 
Vats  lined  with  lead,  on  the  other  hand,  remain  tight  and  have 
the  advantage  that  the  baths  can  be  boiled  in  them  by  means 
of  steam  introduced  through  a  lead  coil  in  the  vats. 

For  large  baths  containing  potassium  cyanide  holders  of  brick 
laid  in  cement  may  also  be  used,  or  holders  of  boiler-plate  lined 
with  a  layer  of  cement. 

A  very  useful  vat  is  one  of  iron  enameled  with  white  acid- 
proof  enamel.  Such  vats  are  made  in  different  shapes  and 
sizes  up  to  5^  feet  long,  24  inches  wide  and  19  inches  deep.. 

For  gold  and  other  solutions  an  agate  vessel  is  recom- 
mended, this  material  standing  cyanide  solutions,  acids,  etc. 

The  vats  for  heating  baths  are  best  made  of  enameled  iron 
or  of  wood  lined  with  sheet  lead.  Stoneware  vats  do  not  bear 
heating. 

It  is  advantageous  to  provide  the  narrow  sides  of  the  vats 
with  semicircular  notches  for  the  conducting  rods  to  rest  in,  to 
prevent  their  rolling  away.  When  using  stoneware  vats  the 


ELECTRO-DEPOSITION    OF   METALS. 


conducting  rods  are  laid  directly  upon  the  vats.  Vats  of  other 
material  must  be  provided  with  an  insulated  rim  of  wood,  or 
the  rods  are  insulated  by  pushing  a  piece  of  rubber  hose  over 
their  ends.  According  to  the  size  of  the  bath,  3,  5,  7,  or  more 
conducting  rods,  best  of  pure,  massive  copper,  are  used. 

To  secure  the  uniform  coating  of  the  objects  with  metal  they 
must  be  surrounded  as  much  as  possible  by  anodes,  i.  e.,  the 
positive  pole  plates  of  the  metal  which  is  to  be  deposited.  For 

FIG.  58. 


No. 


No.  2. 


No.  4. 


flat  objects  it  suffices  to  suspend  them  between  two  parallel 
rows  of  anodes,  the  most  common  arrangement  being  to  place 
three  rods  across  the  bath,  the  two  outermost  of  which  carry 
the  anodes,  while  the  objects  are  secured  to  the  centre  rod. 
For  wide  baths  five  conducting  rods  are  frequently  used,  but 
they  should  always  be  so  arranged  that  a  row  of  objects  is  be- 
tween two  rows  of  anodes.  The  arrangement  frequently  seen 
with  four  rods  across  the  baths,  of  which  the  outermost  carry 
anodes,  and  the  other  two  objects,  is  irrational  if  the  objects  are 


ELECTRO-PLATING   ESTABLISHMENTS. 


lO/ 


FIG.  59.      FIG.  60. 


to  be  uniformly  plated  on  all  sides,  because  the  sides  turned 
towards  the  anodes  are  coated  more  heavily  than  those  sus- 
pended opposite  to  the  other  row  of  objects. 

For  large  round  objects  it  is  better  to  entirely  surround  them 
with  anodes,  if  it  is  not  preferred  to  turn  them  frequently,  so 
that  all  sides  and  portions  gradually  feel  the  effect  of  the  im- 
mediate neighborhood  of  the  anodes.  (See  "  Nickeling.") 

For  objects  to  be  plated  on  one  side  only  the  centre  rod  may 
be  used  for  the  anodes,  and  the  two  outer  ones  for  the  objects ; 
the  surface  to  be  plated  being,  of  course,  turned  toward  the 
anodes. 

The  rods  carrying  the  anodes,  as  well  as  those  carrying  the 
objects,  must  be  well  connected  with  each  other,  which  is 
effected  by  means  of  binding  posts  and  screws  of  the  improved 
forms  shown  in  Fig.  58,  Nos.  I  and  2  being  rod  connections 
for  tanks.  No.  2,  or  double  connection,  is  a  very  convenient 
form  as  it  can  be  adapted  to  so  very 
many  changes.  The  three-way  connec- 
tion, No.  3,  is  so  well  known  that  it 
hardly  needs  an  explanation. 

The  anodes  are  suspended  from  the 
cross  rods  by  strong  hooks  of  the  same 
metal,  so  that  they  can  be  entirely  im- 
mersed in  the  bath  (Fig.  59)  ;  hooks  of 
another  soluble  metal  would  contaminate 
the  bath  by  dissolving  in  it,  and  this 
must  be  strictly  avoided,  as  it  would 
cause  all  sorts  of  disturbances  in  the  correct  working  of  the 
bath.  In  case  hooks  of  another  metal,  except  platinum,  are 
used,  the  anodes  must  be  hung  so  that  they  project  above  the 
surface  of  the  liquid,  and  the  hooks  not  being  immersed  are, 
therefore,  not  liable  to  corrosion ;  but  the  anodes  are  then  not 
completely  used  up,  the  portion  dipping  in  the  solution  being 
gradually  dissolved,  whilst  the  portion  projecting  above  the 
fluid  remains  intact.  Instead  of  wire  hooks,  strips  of  the  same 
metal  as  the  anodes  and  fastened  to  them  by  a  rivet  may  also 
be  used  (Fig.  60). 


108  ELECTRO-DEPOSITION   OF   METALS. 

For  suspending  the  objects  lengths  of  soft  pure  copper  wire, 
technically  called  slinging  wires,  are  used.  They  are  simply 
suitable  lengths  of  copper  wire  of  a  gauge  to  suit  the  work  in 
hand,  wire  of  No.  20  Birmingham  wire  gauge  (see  Chapter 
XVIII. ,  "Useful  Tables")  being  generally  employed  for  such 
light  work  as  spoons,  forks,  and  table  utensils.  Wire  of  a  larger 
diameter  should  be  employed  for  large  and  heavy  goods.  The 
immersed  ends  of  these  wires  becoming  coated  with  the  metal 
which  is  being  deposited,  they  should  be  carefully  set  aside 
each  time  after  use,  and  when  the  deposit  gets  thick  it  should 
be  stripped  off  in  stripping  acid,  and  the  wire  afterwards  an- 
nealed and  straightened  for  future  use. 

To  keep  the  rods  clean  and  to  protect  them  from  the  fluid 
draining  off  from  the  articles  when  taken  from  the  bath,  it  is  ad- 
visable to  cover  them  with  a  roof  of  strips  of  wood  (//\),  or  a 
semi-circular  strip  of  zinc  coated  with  ebonite  lacquer;  by  this 
means  the  frequent  scouring  of  the  rods,  which  otherwise  is 
necessary  in  order  to  secure  a  good  contact  with  the  hooks  of 
the  anodes,  is  done  away  with. 

The  plating  solutions,  briefly  called  baths,  will  be  especially 
discussed  in  speaking  of  the  various  electro-plating  processes.  It 
still  remains  to  consider  the  cleansing  and  rinsing  apparatuses. 
Every  electro-plating  establishment,  no  matter  how  small,  re- 
quires at  least  one  tub  or  vat  in  which  the  objects  can  be  rubbed 
or  brushed  with  a  suitable  agent  in  order  to  free  them  from 
grease.  This  is  generally  done  by  placing  a  small  kettle  or 
stoneware  pot  containing  the  cleansing  material  at  the  right-hand 
side  of  the  operator  alongside  the  vat  or  tub.  Across  the  latter, 
which  is  half  filled  with  water,  is  laid  a  board  of  soft  wood  cov- 
ered with  cloth,  which  serves  as  a  rest  for  the  objects  previously 
tied  to  wires.  The  objects  are  then  scrubbed  with  a  brush,  or 
rubbed  with  a  piece  of  cloth  dipped  in  the  cleansing  agent.  The 
latter  is  then  removed  by  rinsing  the  objects  in  the  water  in  the 
tub  and  drawing  them  through  water  in  another  tub.  By  this 
cleansing  process  a  thin  film  of  oxide  is  formed  upon  the  metals, 
which  would  be  an  impediment  to  the  intimate  union  of  the 


ELECTRO-PLATING   ESTABLISHMENTS.  109 

electro-deposit  with  the  basis-metal.  This  film  of  oxide  has  to 
be  removed  by  dipping  or  pickling,  for  which  purpose  another 
vat  or  tub  containing  the  pickle,  the  composition  of  which  varies 
according  to  the  nature  of  the  metal,  has  to  be  provided.  After 
dipping,  the  objects  have  to  be  again  thoroughly  rinsed  in  water 
to  free  them  from  adhering  pickle,  so  that  for  the  preparatory 
cleansing  processes  three  vessels  with  water,  which  has  to  be 
frequently  renewed,  as  well  as  the  necessary  pots  for  pickling 
solutions,  have  to  be  provided.  In  case  the  vat  for  cleansing  the 
articles  or  the  box-like  table  (see  Fig.  66)  is  provided  with  a 
rose-jet,  under  which  the  objects  are  rinsed,  the  other  vats  are 
not  required. 

After  having  received  the  electro-deposit  the  .objects  have  to 
be  again  rinsed  in  cold  water,  which  can  be  done  in  one  of  the 
three  vats  or  with  the  rose-jet,  and  finally  have  to  be  immersed 
in  hot  water  until  they  have  acquired  the  temperature  of  the 
latter.  How  the  water  is  heated  makes  no  difference,  and  depends 
on  the  size  of  the  establishment.  The  heated  objects  are  then 
immediately  dried  in  a  box  filled  with  dry,  fine  sawdust — that  of 
maple,  poplar,  or  other  wood  free  from  tannin  being  suitable  for 
the  purpose. 

B.  Arrangements  with  dynamo-electric  machines. — For  setting 
up  and  running  the  machines  the  following  rules  are  to  be  ob- 
served. Larger  machines  are  to  be  screwed  to  square  wooden 
joists  resting  upon  a  solid  brick  foundation  about  six  inches 
above  the  floor;  smaller  machines  may  be  placed  upon  and 
fastened  to  strong  tables  secured  to  the  floor  or  wall.  The  prin- 
cipal point  is  that  the  foundation  or  table  is  not  subjected  to 
shocks  which  would  be  transferred  to  the  machines  and  cause, 
by  the  vibration  of  the  brushes,  a  larger  formation  of  sparks, 
and  consequent  greater  wear  of  certain  portions  of  the  machine. 
Foundations  about  8  inches  wider  on  each  side  than  the  machine 
and  built  of  brick  and  cement  have  been  found  most  suitable. 
If  possible,  the  machines  should  be  located  in  the  neighborhood 
of  the  baths  they  are  to  feed,  since  the  greater  the  distance  from 
the  bath  at  which  they  are  placed  the  larger  the  cross-section 


IIO  ELECTRO-DEPOSITION   OF   METALS. 

of  the  principal  conducting  wire  must  be,  and  the  more  trouble- 
some the  regulation  of  the  current  will  prove,  provided  it  is  not 
intended  to  place  another  resistance  board  just  in  front  of  the 
bath,  which  is  the  best  plan  for  regulating  the  curreut  with  the 
greatest  nicety. 

It  is  best  to  set  the  dynamo  in  motion  by  means  of  a  gearing 
with  loose  and  fast  pulley  so  as  to  render  a  gentle  engaging  of 
the  machine  possible,  and  not  directly  from  the  fly-wheel  of  the 
motor,  whereby  in  consequence  of  the  jumping  and  dragging 
of  the  belt  it  is  apt  to  run  less  regularly.  The  bearings  should 
be  kept  well  lubricated,  best  with  automatic  oilers  filled  with 
good  lubricating  oil.  The  stated  number  of  revolutions  per 
minute  should  not  be  exceeded,  since  by  the  stronger  current 
thereby  generated  the  machine  might  become  very  hot  and 
suffer  injury.  On  the  other  hand,  when  a  weaker  current  is 
required,  the  machine  may  be  run  more  slowly  than  the  maxi- 
mum performance  with  the  prescribed  number  of  revolutions. 
The  brushes  which  conduct  the  current  from  the  commutator 
should  be  firmly  secured  in  their  holders  by  means  of  screws, 
and  the  levers  pressing  them  by  means  of  spiral  springs 
against  the  commutators  must  be  fixed  so  that  the  brushes 
securely  and  uniformly  slide  upon  them ;  pressing  the  brushes 
too  tightly  against  the  commutators  should,  however,  be 
avoided.  While  the  machine  is  running  the  brushes  should 
not  be  lifted  off,  since  the  large  sparks  thereby  produced 
strongly  attack  the  brushes  and  the  commutator,  and  this 
favorite  amusement  of  the  workmen  should  be  strictly  for- 
bidden. 

When  the  machine  is  for  the  first  time  set  in  motion,  the 
commutator  should  be  gone  over  with  a  smooth  file  or  emery 
paper  to  remove  any  projections  of  the  insulation  between  the 
metallic  plates,  which  readily  swell  when  the  machine  stands  in 
a  damp  place.  The  commutator  should  also  daily  be  freed,  by 
wiping,  from  copper-dust,  and  if  after  some  time  it  wears 
unevenly,  be  made  smooth  with  a  file. 

The  inductor  ring  should  at  least  once  every  week  be  cleaned 


ELECTRO-PLATING   ESTABLISHMENTS.  Ill 

from  copper-dust  by  means  of  a  small  bellows  or  other  instru- 
ment. Movable  articles  of  iron  and  steel  should  be  kept  away 
from  the  machine  when  running,  as  they  might  be  attracted  by 
the  portions  of  the  machine  which  have  become  strongly 
magnetic. 

The  object-  and  anode-wires  must  be  insulated  from  each 
other,  as  well  as  from  the  ground  and  damp  brick-work  by  dry 
wood  or  porcelain,  and  the  places  of  junction  kept  bright. 

The  employment  of  special  wire-carriers,  of  the  form  shown 
in  Fig.  6 1,  is  advisable.  They  consist  of  cast-iron  arms,  pro- 
vided on  the  ends  with  a  case,  between  the  lower  and  upper 
cover  of  which  are  disks  of  hard  rubber. 

To  regulate  the  current  resistance  boards  or  current- regu- 
lators are  used.  They  are  constructed  according  to  the  same 
principles  as  those  described  under  "  Arrangement  with  Ele- 
ments "  (p.  89),  only  the  spirals  are  longer  and  of  a  larger 
cross-section,  and  the  entire  instrument  is  stronger.  Instead  of 
upon  wood,  the  contact  buttons  are  mounted  upon  slate  plates, 
as  wood  would  be  carbonized  by  the  spirals  becoming  hot. 

In  case  one  machine  has  to  feed  several  baths  of  dissimilar 
nature  and  composition,  the  regulation  of  the  current  for  all  the 
baths  in  the  main  conducting  wire  is  not  feasible  on  account  of 
the  different  resistances  ;   and  it  will  be  neces- 
sary to  place  a  resistance  board  in   front  of  FlG*  6l< 
every  bath.     With  dynamos  of  the  Schuckert 
and  Lahmeyer  type,  which  are  very  practical, 
it  will  be  further  necessary  to  place  a  resist- 
ance   board    (the    resistance    board    of   the  *^- 
dynamo)  in  the  windings  of  the  machine,  in 
order  to  be  enabled  to  generate  more  or  less 
current,  as  may  be  required,  and  to  avoid  an  unnecessary  con- 
sumption of  power.     From   the   scheme  Fig.  62,   for  such  a 
machine,  with  its  auxiliary  apparatus,  the  main  conducting  wire 
and  a  few  baths,  the  reader  will  readily  see  what  is  required. 

The  dynamo  resistance  board  will  have  to  be  placed  so  that 
the  machine  yields  somewhat  more  current  than  with  due  con- 


TK*. 


112 


ELECTRO-DEPOSITION    OF    METALS. 


sideration  to  the  object-area  is  required  for  all  the  baths,  while 
the  supply  of  current  for  each  bath  is  regulated  by  the  resist- 
ance board  placed  in  front  of  it.  In  the  scheme  Fig.  62  are 


i  + 


ELECTRO-PLATING   ESTABLISHMENTS.  113 

sketched  two  further  instruments  for  measuring  the  quantity 
and  the  electro-motive  force  of  the  current ;  by  the  first,  called 
the  amperemeter,  or  better  ammeter,  the  whole  current-strength 
can  be  directly  read  off  in  amperes ;  and  by  the  other,  called 
the  voltmeter,  the  electro-motive  force  or  tension  in  volts.  The 
ammeter  is  placed  in  one  conducting  wire  only,  either  in  that 

FIG.  63. 


f 


of  the   object   or   of  the   anodes,  while   the  voltmeter   is  con- 
nected with  both,  one  setting-screw  being  joined,  on  the  points 


114  ELECTRO-DEPOSITION    OF   METALS. 

where  the  tension  is  to  be  measured,  to  the  object-wire  by  a 
O.O39-inch  thick  copper  wire,  and  the  other  to  the  anode  wire. 
In  the  sketch  (Fig.  62),  the  voltmeter  being  directly  in  contact 
with  the  poles  of  the  machine  will  indicate  the  tension  produced 
by  it.  This  mode  of  placing  the  measuring  instruments  is,  how- 
ever, not  suitable  for  establishments  using  baths  of  different 
compositions  and  different  resistances  ;  in  such  case  the  tension 
must  be  measured  on  the  bath  itself,  and  consequently  the  volt- 
meter has  to  be  placed  in  the  conducting  wire  between  the  re- 
sistance board  of  each  bath  and  the  bath  itself.  However,  for  a 
large  establishment,  using  many  baths,  it  would  be  quite  an  item 
of  expense  to  provide  each  bath  with  a  special  voltmeter.  But 
this  is  not  necessary,  one  voltmeter  sufficing  for  three,  four,  or 
even  more  baths.  In  order  conveniently  to  read  off  on  the 
voltmeter  the  tension  of  the  current  passing  into  one  of  these 
baths  a  shunt  is  required,  the  coustruction  of  which  is  seen  from 
Figs.  63  and  64. 

Fig.  64. 


Fig.  63  shows  the  coupling  of  the  main  object-wire  ( — ) 
and  the  main  anode- wire  (  +  ),  with  the  resistance  boards  Rv 
and  RV  the  voltmeter  V,  the  shunt  £/",  and  the  two  baths. 


ELECTRO-PLATING   ESTABLISHMENTS.  115 

In  Fig.  64  the  coupling  is  enlarged,  and  upon  this  the  fol- 
lowing description  is  based  :  Suppose  the  main  object-wire  and 
anode-wire  to  be  connected  with  the  corresponding  poles  of  a 
dynamo-machine  or  a  battery,  which  for  the  sake  of  a  clearer 
view  is  omitted  in  the  illustration.  The  shunt  U  consists  of  a 
brass  handle,  mounted  with  a  brass  foot,  upon  a  board ;  in  the 
foot  is  a  screw,  with  which  is  connected  by  a  o.O39-inch  thick 
copper-wire  one  of  the  pole-screws  of  the  voltmeter.  The 
brass  handle  drags  with  spring  pressure  upon  contact  buttons 
connected  by  copper  wire  with  the  setting  screws  I,  2,  3,  4,  5 
(upon  the  shunt  board),  which  serve  for  the  reception  of  the 
o.O39-inch  thick  insulated  wires  i,  2,  3,  4,  for  measuring  the 
tension,  which  branch  off  from  the  various  baths  or  resistance 
boards.  The  other  pole-screw  of  the  voltmeter  is  directly  con- 
nected with  the  main  anode-wire.  From  the  main  object-wire, 
a  wire,  whose  cross-section  depends  on  the  strength  of  the 
working  current,  passes  to  the  screw  marked  " strong"  of  the 
resistance  board  Rl ;  the  screw  marked  "  weak  "  of  the  resist- 
ance board  R1  is  connected  by  a  correspondingly  stout  wire 
with  the  object-wire  of  bath  I,  and  at  the  same  time  with  the 
binding-screw  I  of  the  shunt.  The  resistance  board  R2,  of 
the  bath  II,  is  in  the  same  manner  connected  with  the  main 
object-wire,  the  bath,  and  the  binding-screw  2  of  the  shunt; 
also  the  resistance  boards  R3  and  R4  of  the  baths  III  and  IV, 
which  are  not  shown  in  the  illustration.  With  the  main  anode- 
wire  each  bath  is  directly  connected  by  leading  the  current  to 
an  anode- rod  of  the  bath  by  means  of  binding-screws  and  a 
stout  copper  wire,  and  establishing  a  metallic  connection  be- 
tween this  anode-rod  and  the  next  one.  However,  instead  of 
connecting  both,  the  current  may  also  be  led  from  the  main 
anode-wire  to  each  anode-rod. 

In  the  illustration,  the  handle  of  the  shunt  rests  upon  the 
second  contact-button  to  the  left,  which  is  connected  with  the 
binding-screw  2  of  the  board.  In  the  latter  is  secured  the  wire 
for  measuring  the  tension  of  the  resistance  board  R^ ;  and  hence 
the  voltmeter  V  will  indicate  the  tension  of  the  current  in  bath 


Il6  ELECTRO-DEPOSITION    OF   METALS. 

II.  Suppose  bath  II  is  full  of  objects,  and  with  the  position  of 
the  handle  of  the  resistance  board  at  "  weak,"  as  shown  in  the 
illustration,  the  voltmeter  indicates  1.5  volts,  while  the  most 
suitable  tension  for  the  bath  is  2.5  volts,  the  handle  of  the  re- 
sistance board  is  turned  to  the  left  until  the  needle  of  the  volt- 
meter indicates  the  desired  2.5  volts. 

By  turning  the  handle  of  the  shunt  U  to  the  left,  so  that  it 
rests  upon  the  contact-button  i,  the  measuring  wire  of  bath  II 
is  thrown  out,  and  the  voltmeter  indicates  the  tension  in  bath  I. 
If  the  handle  rests  upon  contact-button  3,  the  tension  in  bath 
III  is  indicated,  and  so  on. 

In  working  the  different  baths  in  a  larger  establishment,  each 
bath  is  best  directly  fed  from  the  main  conducting  wire  after  the 
current  has  been  brought  to  the  proper  strength  by  the  resist- 
ance board.  Coupling  the  baths  one  after  another  so  that  the 
current  passes  from  one  bath  to  the  other  is  only  practicable  for 
metallurgical  processes — gaining  of  metals — where  every  bath 
contains  the  same  area  of  objects  and  anodes,  has  the  same  re- 
sistance, and  works  under  the  same  conditions. 

Fig.  65  shows  the  ground  plan  of  an  electro-plating  establish- 
ment. NN1  is  a  dynamo-electric  machine,  with  300  amperes  at 
4  volts'  tension.  The  resistance  board  belonging  to  the  machine, 
which  is  placed  in  the  conductor,  is  indicated  by  No.  I,  and  is 
screwed  to  the  wall.  The  main  conductors,  marked  —  and  -f ,  run 
along  the  wall,  from  which  they  are  separated  by  wood,  and  con- 
sist of  rods  of  pure  copper  0.59  inch  in  diameter.  The  rods  are 
connected  with  each  other  by  brass  coupling-boxes  with  screws. 
From  the  negative  pole  and  the  positive  pole  of  the  machine  to 
the  objeet-wire  and  anode-wire  lead  two  wires,  each  0.27  inch 
in  diameter ;  one  end  of  each  is  bent  to  a  flat  loop  and  secured 
under  the  pole  screws  of  the  machine,  while  the  other  ends  are 
screwed  into  the  second  bore  of  the  binding-screws  screwed 
upon  each  conductor.  To  the  right  and  left  of  the  machine  the 
baths  are  placed  ;  Zn,  indicating  zinc  bath  ;  Ni  Ni,  nickel  baths, 
Ku,  copper  cyanide  bath ;  Mg,  brass  bath ;  5  K,  acid  copper 
bath ;  Si,  silver  bath ;  and  Go,  gold  bath.  Each  of  the '  first- 


ELECTRO-PLATING   ESTABLISHMENTS. 


117 


named  five  baths  has  its  own  resistance  board,  designated  by  2, 
3,  4,  5,  6.     However,  before  reaching  the  acid  copper  bath,  and 

FIG.  65. 


/  7///../T77 


V//////7-7 


Jl8  ELECTRO-DEPOSITION    OF   METALS. 

the  silver  and  gold  baths,  the  current  is  conducted  through  two 
resistance  boards,  7  and  8.  Since  these  baths  require  a  current 
of  only  slight  electro-motive  force,  it  is  necessary  to  place  two, 
and  in  many  cases  even  three  or  four  resistance  boards,  one 
after  another,  unless  it  be  preferred  to  feed  these  baths  with  a 
special  machine  of  less  tension. 

From  Fig.  65  it  will  be  seen  that  the  current  weakened  by  the 
resistance  boards  7  and  8  serves  for  conjointly  feeding  the  acid- 
copper,  silver,  and  gold  baths.  Hence,  practically,  only  one 
bath  can  be  allowed  to  work  at  one  time,  as  otherwise  each  bath 
would  have  to  be  provided  with  as  many  resistance  boards  as 
would  be  required  for  the  reduction  of  the  tension.  For  want 
of  space  the  gold  bath  is  placed  in  the  sketch  be'hind  the  silver 
bath ;  but  as  their  resistance  is  not  the  same,  they  must  also  be 
placed  parallel.  t 

The  coupling  of  the  voltmeter  and  shunt  is  omitted  in  the 
illustration.  Their  arrangement  will  be  understood  from 
Fig.  63. 

L  is  the  lye-kettle ;  it  serves  for  cleansing  the  objects  by 
means  of  hot  caustic  potash  or  soda-lye  from  grinding  and 
polishing  dirt  and  oil.  '  Instead  of  the  preparatory  cleansing 
with  hot  lye,  which  saponifies  the  oils,  the  objects  may  be 
brushed  off  with  benzine,  oil  of  turpentine,  or  petroleum,  the 
principal  thing  being  the  removal  of  the  greater  portion  of 
the  grease  and  dirt,  so  that  the  final  cleansing,  which  is 
effected  with  lime  paste,  may  not  require  too  much  time  and 
labor.  It  is  also  advisable  to  cleanse  the  objects,  in  one  way 
or  the  other,  immediately  after  grinding,  as  the  dirt,  which 
forms  a  sort  of  solid  crust  with  the  oil,  is  difficult  to  soften  and 
to  remove  when  once  hard.  The  table  for  freeing  the  articles 
from  grease  stands  alongside  the  lye-kettle,  and  is  shown  in 
perspective  in  Fig.  66.  It  consists  of  a  box  with  legs,  which 
is  divided  by  four  partitions  into  two  large  divisions,  A  and  B, 
and  three  smaller  ones,  C,  D,  and  E.  The  separate  divisions 
are  lined  with  sheet  lead.  Across  divisions  A  and  B  boards 
covered  with  cloth  are  laid,  upon  which  the  articles  are  brushed 


ELECTRO-PLATING   ESTABLISHMENTS. 


119 


for  the  final  cleansing  with  lime  paste.  Over  each  of  these 
divisions  is  a  rose-jet,  provided  with  a  cock,  under  which  the 
articles  are  rinsed  with  water.  The  discharge  pipes  from  A  and 
B  are  provided  with  valves,  and  are  tightly  soldered  into  the 
bottom  of  the  box.  Of  the  smaller  partitions,  D  serves  for 

Fig.  66. 


the  reception  of  the  lime  paste,  while  C  and  E  each  contain 
two  pots  or  small  stoneware  vats  with  pickling  fluid.  In  Fig. 
65  these  vats  are  indicated  by  1 1  and  12.  The  two  marked  I  T 
contain  dilute  sulphuric  acid  for  pickling  iron  and  steel  articles, 
while  those  marked  12  contain  dilute  potassium  cyanide  solu- 
tion for  pickling  copper  and  its  alloys,  and  Britannia,  etc.  For 
cleansing  smaller  articles,  four  men  can  at  one  time  work  on 
such  a  table ;  but  for  cleansing  larger  articles  only  two.  The 
advantages  of  such  a  box-table  are  that  everything  is  handy 
together ;  that  the  pickle,  in  case  a  pot  should  break,  cannot 
run  over  the  floor  of  the  workshop ;  and  that  the  latter  is  not 
spoiled  by  pickle  dropping  from  the  objects.  The  small  box 
K,  on  the  side  of  the  table,  serves  for  the  reception  of  the 
various  scratch-brushes. 

Between  the  lye-kettle  L  and  the  box-table  in  Fig.  65  is  a 
frame,  14,  for  the  reception  of  brass  and  copper  wire  hooks  of 
various  sizes  and  shapes  suitable  for  suspending  the  objects  in 
the  bath. 


120  ELECTRO -DEPOSITION   OF   METALS. 

The  reservoir  W,  filled  with  water,  standing  in  front  of  the 
machine,  serves  for  the  reception  of  the  cleansed  and  pickled 
objects,  if  for  some  reason  or  another  they  cannot  be  im- 
mediately brought  into  the  bath. 

H  W  is  the  hot  water  reservoir  in  which  the  plated  objects 
are  heated  to  the  temperature  of  the  hot  water,  so  that  they 
may  quickly  dry  in  the  subsequent  rubbing  in  the  sawdust  box 
Sp.  Before  polishing  the  deposits,  iron  and  steel  objects  are 
thoroughly  dried  in  the  drying  chamber  T  (Fig.  65),  heated 
either  by  steam  or  direct  fire.  By  finally  adding  to  the  appli- 
ances a  large  table,  13,  for  sorting  and  tying  the  objects  on  the 
copper  wires,  and  a  few  shelves  not  shown  in  the  illustration, 
everything  necessary  for  operating  without  disturbance  will 
have  been  provided. 

If  possible  the  plating-room  should  be  on  the  ground  floor 
and  where  it  will  receive  the  best  light  and  ventilation,  both 
being  essential  to  good  work.  The  room  must  also  be  provided 
with  facilities  for  obtaining  water  and  steam,  as  much  of  the  work 
in  plating  is  in  preparing  the  article  for  plating  by  scouring  and 
rinsing,  and,  with  convenient  facilities  in  doing  this,  the  cost  is 
reduced  and  better  work  accomplished.  Where  a  plating 
plant  is  required,  provision  should  be  made  for  extension  or  de- 
velopment of  trade.  The  dynamo  should  also  be  larger  than 
absolutely  necessary,  as  a  plant  can  then  be  enlarged  as  required 
by  adding  one  or  more  tanks,  the  other  appliances  remaining 
the  same. 

Fig.  67  shows  a  plating-room  arranged  by  the  Hanson  &  Van 
Winkle  Co.,  of  Newark,  N.  J.  The  arrangement  will  be  readily 
understood  from  the  illustration,  so  that  a  detailed  description 
is  not  necessary. 

What  has  been  said  in  the  preceding  section  in  regard  to  the 
conducting  wires,  vats,  conducting  rods,  anodes,  etc.,  also  ap- 
plies to  establishments  using  electro-dynamo  machines. 

In  calculating  the  thickness  of  the  conducting  wires  for  dyna- 
mos, I  square  millimetre  (o.ooi  square  inch)  of  conducting 
cross-section  is  to  be  allowed  for  every  3  amperes  for  so-called 
short  circuits  up  to  20  metres  (21.87  yards).  This  is  valid  for 


ELECTRO-PLATING  ESTABLISHMENTS. 


121 


currents  up  to   500  amperes;   for  longer  circuits  I  j£  to  2  am- 
peres are  calculated  for  the  square  millimetre  of  conducting 

cross-section. 

FIG.  67. 


PLAT/M6 

D£S/G 
THE  HAM50M  &  VAN  WINKL  E  CO.. 

£S 
CHICAGO  MEWARK,N.J..  t/£tV  YORK 


CHAPTER  V. 

TREATMENT   OF   METALLIC    ARTICLES. 

THE  objects  having  to  undergo  both  a  mechanical  and  chem- 
ical preparation,  each  of  them  will  be  considered  separately. 

A.  Mechanical  Treatment. 

I.  Before  electro-plating. — If  the  objects  are  not  to  be  electro- 
plated while  in  a  crude  state,  which  is  but  rarely  feasible,  the 
mechanical  treatment  consists  in  imparting  to  them  a  cleaner 
surface  by  scratch-brushing,  or  a  smoother  and  more  lustrous  one 
by  grinding  and  polishing.  It  may  here  be  explicitly  stated 
that  scratch-brushing  of  electro-plated  objects  is  not  to  be  con- 
sidered a  part  of  their  preparation,  since  such  scratch-brushing 
is  executed  in  the  midst  of  or  after  the  electro-plating  process, 
its  object  being  to  effect  a  change  of  the  electro-deposition  in 
more  than  one  direction,  and  not  the  cleansing  of  the  surface 
of  the  metallic  base.  The  following  directions,  therefore,  apply 
only  to  scratch-brushing  of  objects  not  electro -plated.  The 
scratch-brushing  of  electro-depositions  will  be  considered  later 
on.  In  regard  to  grinding,  we  have  to  deal  with  the  subject 
only  in  so  far  as  it  relates  to  smoothing  rough  surfaces  by  the 
use  of  grinding  powders  possessing  greater  hardness  than  the 
metal  to  be  ground ;  with  grinding  in  the  sense  of  instrument- 
grinding,  the  primary  object  of  which  is  to  provide  the  instru- 
ment with  a  cutting  edge,  we  have  nothing  to  do. 

As  some  platers  seem  to  have  wrong  ideas  regarding  the 
electro  plating  process,  it  may  here  be  mentioned  that  the  de- 
posit is  formed  exactly  in  correspondence  with  the  surface  of 
the  basis  metal.  If  the  latter  has  been  made  perfectly  smooth 
by  grinding  and  polishing,  the  deposit  will  be  of  the  same 

(122) 


TREATMENT    OF   METALLIC   ARTICLES. 


123 


nature  ;  but  if  the  basis-surface  is  rough,  the  deposit  also  will  be 
rough.  Hence  it  is  wrong  to  suppose  that  by  electro-plating 
a  rough  surface  can  be  converted  into  a  lustrous  one,  and  that 
pores  or  holes  in  the  basis-metal  can  be  filled  by  plating.  In 
order  to  obtain  a  deposit  which  is  to  acquire  high  lustre  by 
polishing,  it  is  absolutely  necessary  to  bring  the  basis  into  a 
polished  state  by  mechanical  treatment.  In  doing  this  it  is  not 
necessary  to  go  so  far  as  to  produce  high  lustre,  but  fine 
scratches  which  would  be  an  impediment  to  attaining  high 
lustre  after  plating  must  be  removed. 

Scratch-brushing  may  be  effected  either  by  hand  or  by  a 
scratch-brush  lathe.  In  the  first  place  scratch-brushes  of  more 
or  less  hard  brass  or  steel  wire,  according  the  hardness  of  the 
metal  to  be  manipulated,  are  used.  Various  forms  of  brushes 
are  employed,  the  most  common  ones  being  shown  in  the 
accompanying  illustrations  (Figs.  68  to  76.) 


FIG.  68. 


FIG.  69. 


FIG.  70. 


FIG.  71. 


Fig.  75  shows  swing  brushes  for  frosting  or  satin  finish,  with 
lour  knots  of  medium  brass  or  steel  wire,  and  Fig.  76  the 
plater's  lathe  goblet  scratch-brush. 


I24 


ELECTRO-DEPOSITION   OF   METALS. 


In  scratch  brushing  it  is  recommended  to  remove,  or  at  least 
to  soften,  the  uppermost  hard  and  dirty  crust  (the  scale)  by 
immersing  the  objects  in  a  pickle,  the  nature  of  which  depends 
on  the  variety  of  metal,  so  that  a  complete  removal  of  all  im- 


FIG.  72. 


FIG.  73. 


FIG.  74. 


FIG.  76. 


FIG.  75. 


purities  and  non- metallic  substances  may  be  effected  by  means 
of  the  scratch-brush  in  conjunction  with  sand,  pumice-stone, 
powder,  or  emery.  The  work  is  complete  only  when  the 
article  shows  a  clean  metallic  surface,  otherwise  the  brushing 
(scouring)  must  be  continued.  Scratch-brushes  must  be  care- 
fully handled  and  looked  after,  and  their  wires  kept  in  good 
order.  When  they  become  bent  they  have  to  be  straightened, 
which  is  most  readily  effected  by  several  times  drawing  the 
brush,  held  in  a  slanting  position,  over  a  sharp  grater  such  as 
is  used  in  the  kitchen.  By  this  means  the  wires  become  dis- 
entangled and  straightened  out. 

Hand  scratch-brushing  being  slow  and  tedious  work,  large 
establishments  use  circular  scratch-brushes  which  are  attached 
to  the  spindle  of  a  lathe.  These  circular  brushes  consist  of 
round  wooden  cases  in  which,  according  to  requirement,  I  to 
6  or  more  rows  of  wire  bundles  (see  Fig.  77)  are  inserted. 


TREATMENT    OF   METALLIC   ARTICLES.  125 

Brushes  with  wooden  cases  are,  however,  more  suitable  for 
scratch-brushing  deposits  than  for  cleansing  the  metallic  base, 
since  for  the  latter  purpose  a  more  energetic  pressure  is  usually 
applied,  in  consequence  of  which  the  bundles  bend  and  even 
break  off,  if  the  wire  is  anywise  brittle.  For  cleansing  purposes 
a  circular  scratch-brush,  which  the  workman  can  readily  re- 
furnish with  new  bundles  of  wire,  deserves  the  preference.  It 
is  constructed  as  follows:  A  round  iron  disk  about  o.ii  inch 
thick,  and  from  5f  to  7f  inches  in  diameter,  is  provided  in  the 
centre  with  a  hole  so  that  it  can  be  conveniently  placed  upon 
the  spindle  of  the  lathe.  At  a  distance  of  from  0.19  to  0.31 
inch  from  the  periphery  of  the  disk,  holes  0.079  to  o.i  I  inch  in 
diameter  are  drilled,  so  that  between  each  two  holes  is  a  distance 

FIG.  77. 


of  0.15  inch.  Draw  through  these  holes  bundles  of  wire  about 
3.93  inches  long,  so  that  they  project  an  equal  distance  on 
both  sides.  Then  bend  the  bundles  towards  the  periphery, 
and  on  each  side  of  the  iron  disk  place  a  wooden  disk  0.31  to 
0.39  inch  thick.  The  periphery  of  the  wooden  disk,  on  the  side 
next  to  the  iron  disk,  should  be  turned  semi-annular,  so  that 
the  wooden  disks  when  secured  to  the  spindle  press  very  lightly 
upon  the  wire  bundles,  and  the  latter  remain  very  mobile. 
When  a  circular  scratch-brush  constructed  in  this  manner  and 
secured  to  the  lathe  is  allowed  to  make  from  1800  to  2000 
revolutions  per  minute,  the  bundles  of  wire,  in  consequence  of 
the  centrifugal  force,  stand  very  rigid,  but  being  mobile  will 
give  way  under  too  strong  a  pressure  without  breaking  off,  and 
can  thus  be  utilized  to  the  utmost.  When  required,  the  iron 


126  ELECTRO-DEPOSITION   OF   METALS. 

disk  can  be  refurnished  with  wires  in  less  than  half  an  hour. 
An  error  frequently  committed  is  that  the  objects  to  be  cleansed 
are  pressed  with  too  heavy  a  pressure  against  the  wire  brushes. 
This  is  useless,  since  only  the  sharp  points  of  the  wire  are 
effective,  the  lateral  surfaces  of  the  bundles  removing  next  to 
nothing  from  the  articles. 

Brushes. — A  definition  of  these  instruments  is  unnecessary, 
and  we  shall  simply  indicate  the  various  kinds  suitable  to  the 
different  operations. 

The  fire-gilder  employs,  for  equalizing  the  coating  of 
amalgam,  a  long-handled  brush,  the  bristles  of  which  are  long 
and  very  stiff.  The  electro-gilder  uses  a  brush  (Fig.  78)  with 
long  and  flexible  bristles. 

For  scouring  with  sand  and  pumice-stone  alloys  containing 
nickel,  such  as  German  silver,  which  are  difficult  to  cleanse  in 
acids,  the  preceding  brush,  with  smaller  and  stiffer  bristles,  is 
used. 

The  gilder  of  watch-works  has  an  oval  brush  (Fig.  79),  with 
stiff  and  short  bristles  for  graining  the  silver. 

The  galvanoplastic  operator,  for  coating  moulds  with  black- 
lead,  besides  a  number  of  pencils,  uses  also  three  kinds  of  brushes 
— the  watchmaker's  (Fig.  80),  a  hat  brush,  and  a  blacking-brush. 
The  bronzer  uses  all  kinds  of  brushes. 

FIG.  78.  FIG.  79.  FIG.  80. 


Brushes  are  perfectly  freed  from  adherent  grease  by  washing 
with  benzine  or  bisulphide  of  carbon. 

In  large  establishments  engaged  in  electro-plating  cast-iron 
without  previous  grinding,  the  use  of  the  sand-blast  in  place  of 
the  circular  wire  brush  has  been  introduced  with  great  ad- 
vantage. Objects  with  deep  depressions,  which  cannot  be 
reached  with  the  scratch-brush,  as  well  as  small  objects,  which 


TREATMENT    OF   METALLIC   ARTICLES. 


127 


cannot  be  conveniently  held  in  the  hand  and  pressed  against 
the  revolving  scratch-brush,  can  be  brought  by  the  sand-blast 
into  a  state  of  sufficient  metallic  purity  for  the  electro-plating 
process.  However,  while  the  revolving  scratch-brushes  impart 
to  the  objects  a  certain  lustre,  they  acquire  by  the  sand-blast  a 
dead  lustre,  and,  hence,  the  blast  is  also  frequently  used  for  the 
purpose  of  deadening  lustrous  surfaces  to  their  entire  extent,  or 
of  producing  contrasts — for  instance,  dead  designs  upon  a  lus- 
trous ground,  or  vice  versa. 

Fig.    8 1    shows  a  sand-blast.     The    compressed   air,   whose 

FIG.  81. 


pressure  must  be  at  least  equal  to  an  18^  inch  column  of  water, 
passes  through  the  blast-pipe  A  into  a  nozzle  running  horizont- 
ally through  the  machine,  and  carries  away  from  there  a  jet  of 


128  ELECTRO- DEPOSITION   OF   METALS. 

sand,  which  falls  into  the  outflowing  blast  and  is  hurled  upon  the 
objects  placed  under  the  nozzle.  The  objects  rest  upon  sheet- 
iron  plates  or  in  boxes  of  sheet-iron,  which,  moving  at  a  slow 
rate,  pass  under  the  nozzle  ;  the  motion  is  effected  by  the  shafts 
B  B,  with  the  use  of  belts.  To  prevent  dust,  the  machine  is 
encased  in  a  wooden  or  sheet-iron  case,  a  few  windows  allowing 
a  view  of  the  interior.  The  sand  used  in  blasting  collects  in  a 
box,  and  is  returned  to  the  sand-reservoir  by  an  elevator. 

The  jet  of  sand  acts  not  only  upon  the  upper  side  of  the 
objects,  which  it  strikes  first,  but  also  almost  as  energetically 
upon  the  lower,  so  that,  as  a  rule,  the  cleansing  process  is  com- 
pleted by  one  operation.  Objects  of  a  specially  unfavorable 
shape  must  be  passed  twice  or  three  times  under  the  nozzle. 

Steam-jet  sand  blasts  have  recently  been  constructed,  the 
action  of  which  is  based  upon  the  same  principle.  However, 
in  place  of  compressed  air  a  jet  of  steam  is  used,  the  action  of 
which  is  still  more  rapid. 

If  a  clean  metallic  surface  is  to  be  given  at  one  time  to  a  large 
number  of  small  articles,  such  as  buckles,  steel  beads,  metal 
buttons,  steel  watch-chains,  ferrules,  etc.,  a  tumbling  drum  or 
box  is  frequently  used.  It  generally  consists  of  a  cylindrical  or 
polygonal  box  having  a  side  door  for  the  introduction  of  the 
work,  together  with  sharp  sand  or  emery,  and  is  mounted  hori- 
zontally on  an  axis  furnished  with  a  winch  or  pulley,  so  as  to  be 
revolved  either  by  hand  or  power,  as  may  be  desired.  In  order 
to  prevent  certain  objects,  like  hooks  for  ladies'  dresses  and  the 
like,  from  catching  each  other  and  accumulating  into  a  mass,  a 
number  of  nails  or  wooden  pegs  are  fixed  in  the  interior  of  the 
drum. 

A  very  practical  form  of  tumbling  drum,  in  which  a  change 
of  position  of  the  contents  must  constantly  take  place,  is  shown 
in  Fig.  82.  The  drum  A,  of  wood  or  iron,  is  obliquely  placed 
upon  the  shaft  B.  The  objects  are  introduced  through  the 
door  C.  The  drum  is  revolved  by  a  crank,  or  by  a  belt  by 
means  of  the  pulley  D.  All  portions  of  the  drum  describe 
thereby  ellipses,  the  walls  of  the  drum  being  now  raised  (indi- 


TREATMENT   OF   METALLIC    ARTICLES. 


129 


cated  by  the  dotted  lines)  and  then  lowered,  so  that  the  objects 
in  the  drum  are  in  constant  motion  and  rub  against  each  other. 
By  introducing  together  with  the  objects  a  suitable  polishing 
powder  with  oil  or  water,  such  drums  may  be  used  not  only  for 
the  preparatory  cleansing  of  the  objects,  but  also  for  polishing. 


Fig.  83  shows  the  improved  exhaust  tumbling  barrel  manu- 
factured by  the  Hanson  &  Van  Winkle  Co.,  of  Newark,  N.  J. 
It  will  be  seen  that  the  barrel  is  egg-shaped,  that  it  has  a  sec- 
tion of  exhaust  pipe  connected  to  the  hollow  journal  at  one 
end,  and  a  tight  and  loose  pulley  at  the  other  end.  No  gearing 
whatever  is  used.  The  special  advantages  of  this  tumbling 
barrel  are  found  in  the  egg-shape. 

1 .  It  gives  the  contents  a  double  motion  or  action — from  ends 
to  center  and  from  sides  to  center — causing  a  thorough  mixing 
and  rubbing  together  of  all  the   parts  contained  therein,  clean- 
ing and   polishing  the   contents  better  and  quicker  than   any 
other  form  of  barrel. 

2.  It  requires  less  power,  as  the  end  motion  causes  the  con- 
tents at  the  ends  to  tumble  into  the  center  because  of  their  as- 
suming the  perpendicular  earlier  than  the  parts  at  the  sides. 

3.  It  runs  with  less  noise,  because  the  contents  are  kept  mov- 
ing in  two  directions  at  the  same  time,  doing  away  with  the  in- 
termediate motion  so  noticeable  in  other  forms.     Doing  away 
with  gearing  also  lessens  the  noise. 

The  manufacturers  claim  that  this  barrel  will  do*  double  the 
work  of  any  other  of  the  same  size  in  the  same  length  of  time. 
9 


130 


ELECTRO-DEPOSITION    OF   METALS. 


It  is  lined  with  a  sectional  lining  of  hard  iron,  which  can  be 
cheaply  and  quickly  replaced,  making  the  barrel  as  good  as 
new.  A  current  of  air  is  forced  through  the  barrel  by  an  ex- 
haust fan,  which  removes  the  dust  and  carries  it  out  through 
pipes  arranged  for  the  purpose,  and  the  room  is  kept  perfectly 
free  from  this  nuisance. 

For  ordinary   polishing   the   articles   are    brought    into    the 

FIG.  83. 


tumbling  drums  together  with  small  pieces  of  leather  waste 
(leather  shavings),  and  taken  out  in  one  or  two  days.  How- 
ever, to  produce  an  actually  good  polish  a  somewhat  more 
complicated  method  has  to  be  pursued.  The  articles  are  first 
freed  from  adhering  oxide  by  washing  in  water  containing  5  per 
cent,  of  sulphuric  acid,  rinsed,  and  dried  in  a  drying  chamber 
or  in  a  pan  over  a  fire.  They  are  next  brought  into  the  tumb- 


TREATMENT   OF   METALLIC   ARTICLES.  131 

ling  drum  together  with  the  sharp  sand,  such  as  is  used  in 
glass-making,  and  revolved  for  about  12  hours,  when  they  are 
taken  from  the  drum  and  freed  from  the  admixed  sand  by  sift- 
ing. They  are  then  returned  to  the  drum,  together  with  soft, 
fibrous  sawdust,  to  free  them  from  adhering  sand,  and  at  the 
same  time  to  give  them  a  smoother  surface.  They  are  now 
again  taken  from  the  drum,  freed  from  sawdust  and  returned  to 
the  drum,  together  with  leather  shavings.  They  now  remain 
in  the  drum  until  they  have  acquired  the  desired  polish,  which, 
according  to  the  size  and  shape  of  the  articles  and  the  degree 
of  polish  required,  may  frequently  take  two  weeks  or  more. 
Articles  of  different  shapes  and  sizes  are  best  treated  together, 
time  being  thereby  saved.  The  process  is  also  accelerated  by 
adding  some  fat  oil  to  the  leather  shavings,  which,  of  course, 
must  be  omitted  when,  after  long  use,  the  shavings  have  become 
quite  greasy.  The  drum  should  be  filled  about  half  full,  other- 
wise the  articles  do  not  roll  freely  and  polishing  is  retarded. 
On  the  other  hand,  when  the  drum  is  less  than  half  full  there  is 
danger  of  the  articles  bending,  or  in  case  they  are  hardened, 
for  instance  buckles,  of  breaking. 

For  many  purposes  polishing  in  the  tumbling  drum  is  of  great 
advantage,  since,  independent  of  its  cheapness,  the  sharp  edges 
of  the  articles  are  at  the  same  time  rounded  off.  However, 
with  articles  the  edges  of  which  have  to  remain  sharp,  the 
process  cannot  be  employed. 

The  tumbling  drum  in  which  the  articles  are  treated  with 
sand  cannot  be  used  for  polishing  with  leather  shavings,  it  be- 
ing next  to  impossible  to  free  it  entirely  from  sand.  The 
drums  should  make  from  50  to  70  revolutions  per  minute;  if 
allowed  to  revolve  more  rapidly,  the  articles  take  part  in  the 
revolutions  without  rolling  together,  which,  of  course,  would 
prevent  polishing. 

The  brightening  of  articles  of  iron  and  steel  may  be  simplified 
by  using  water  to  which  I  per  cent,  of  sulphuric  acid  has  been 
added.  The  drum  used  for  the  purpose  must,  of  course,  be 
water-tight.  By  the  addition  of  sand  the  process  is  accelerated. 


132  ELECTRO-DEPOSITION    OF   METALS. 

Nickel  and  copper  blanks  for  coins  are  also  cleansed  in  this 
manner.  They  are  brought  into  the  tumbling  drum,  together 
with  a  pickling  fluid,  and,  when  sufficiently  treated,  are  taken 
out,  rinsed,  dried  in  sawdust,  and  finally  stamped. 

Grinding. — For  grinding  the  objects  for  the  electro-plating 
process,  wooden  disks  covered   with  leather  coated  with  emery 
of   various    degrees    of  fineness  are   almost  exclusively  used. 
The  wooden  disks  are  made  of  thoroughly  seasoned  poplar  in 
the  manner  shown  in  Fig.  84.     The  separate  pieces  are  radially 
glued  together,  and  upon  each  side  in  the 
FlG*  84'  centre  a  strengthening  piece  is  glued  and 

secured  with  screws,  so  that  each  segment 
of  the  wooden  disk  is  connected  with  the 
strengthening  piece.  The  centre  of  the 
disk  is  then  provided  with  a  hole  corres- 
ponding to  the  diameter  of  the  spindle  of 
the  grinding  lathe,  to  which  it  is  secured 
by  means  of  wedges.  The  periphery  as 
well  as  the  sides  is  then  turned  smooth.  A  good  quality  of 
leather  previously  soaked  in  water  and  cut  into  strips  corres- 
ponding to  the  width  of  the  wooden  disk  is  then  glued  to  the 
periphery  of  the  disk,  and  still  further  secured  by  pins  of  soft 
wood.  When  the  glue  is  dry  the  disk  is  again  wedged  upon  the 
spindle  and  the  leather  carefully  turned ;  it  is  then  ready  for 
coating  with  emery. 

For  this  purpose  three  different  kinds  of  emery  are  used,  a 
coarse  quality  (Nos.  60  to  80)  for  preparatory  grinding,  a  finer 
quality  (No.  oo)  for  fine  grinding,  and  the  finest  quality  (No. 
oooo)  for  imparting  lustre.  The  disks  thus  coated  are  termed 
respectively  "  roughing  wheel,"  "  medium  wheel,"  and  "  fine 
wheel."  With  the  first  the  surface  of  the  objects  are  freed  from 
the  rough  crust.  The  coarse-grained  emery  used  for  this  pur- 
pose, however,  leaves  scratches,  which  have  to  be  removed  by 
grinding  upon  the  medium  wheel  until  the  surface  of  the  objects 
shows  only  the  marks  due  to  the  finer  quality  of  emery,  which 
are  in  their  turn  removed  by  the  fine  wheel. 


TREATMENT   OF   METALLIC   ARTICLES.  133 

In  most  cases  brushing  with  a  circular  bristle  brush  may  be 
substituted  for  the  last  grinding,  the  articles  being  moistened, 
with  a  mixture  of  oil  and  emery  No.  oooo.  Care  must  be  had 
not  to  execute  the  brushing,  nor  the  grinding  with  the  finer 
quality  of  emery,  in  the  same  direction  as  the  preceding  grind- 
ing, but  in  a  right  angle  to  it. 

Treatment  of  the  grinding  disks . — The  coating  of  the  roughing 
wheels  with  emery  is  effected  by  applying  to  them  a  good  qual- 
ity of  glue  and  rolling  them  in  a  dry  coarse  emery  powder.  For 
the  medium  and  fine  wheels,  however,  the  emery  is  mixed  with 
the  glue  and  the  mixture  applied  to  the  leather.  When  the  first 
coat  is  dry,  a  second  is  applied,  and  finally  a  third.  The  whole 
is  then  thoroughly  dried  in  a  warm  place.  Before  use,  a  piece 
of  tallow  is  held  to  the  revolving  disk  for  the  purpose  of  impart- 
ing a  certain  greasiness  to  it,  and  in  order  to  remove  any  rough- 
ness due  to  an  unequal  application  of  the  emery  it  is  smoothed 
by  pressing  a  smooth  stone  against  it.  While  the  preparatory 
grinding  upon  the  roughing  wheel  is  executed  dry,  i.  e.,  without 
the  use  of  oil  or  fat,  in  fine  grinding  the  objects  are  frequently 
moistened  with  a  mixture  of  oil  or  tallow  and  the  corresponding 
No.  of  emery.  When  the  layer  of  emery  is  used  up,  the  re- 
mainder is  soaked  with  warm  water  and  scraped  off  with  a  dull 
knife.  The  leather  of  the  disks  on  which  oil  or  tallow  has  been 
used  is  then  thoroughly  rubbed  with  caustic  lime  or  Vienna 
lime*  to  remove  the  greasiness,  which  would  prevent  the  ad- 
herence of  the  layer  of  glue  and  emery  to  be  applied  later  on. 
When  the  leather  is  thoroughly  dry  a  fresh  layer  of  emery  may 
at  once  be  applied. 

Grinding  lathes. — For  use,  the  grinding  disks  or  buffs  are 
wedged  upon  a  conical  cast-steel  spindle  provided  with  a  pulley 
and  working  in  hard-wood  bearings,  as  plainly  shown  in  Fig.  85. 
The  cast-iron  standards  are  screwed  to  the  floor ;  the  wooden 

*  Vienna  lime  is  prepared  from  a  variety  of  dolomite  which  is  first  burned,  then 
slacked,  and  finally  incinerated  for  a  few  hours.  It  consists  of  lime  and  magnesia, 
and  should  be  kept  in  well-closed  cans,  as  otherwise  it  absorbs  carbonic  acid  and 
moisture  from  the  air,  and  becomes  useless. 


134  ELECTRO-DEPOSITION   OF   METALS. 

bearings  can  be  shifted  forward  and  backward  by  wedges  and 
secured  in  a  determined  position  by  a  set  screw,  thus  facilitating 
the  removal  of  the  spindle  after  throwing  off  the  belt.  The  disks 
being  wedged  upon  a  conical  spindle  they  always  run  centrically 
•The  changing  of  the  disks  requires  but  a  few  seconds,  and  on 
account  of  the  slight  friction  of  the  points  of  the  spindle  in  the 
wooden  bearings  the  consumption  of  power  is  very  slight. 

FIG  85. 


To  avoid  the  necessity  of  throwing  off  the  belt  while  changing 
the  grinding  disks,  double  machines  (Fig.  86)  are  used,  the  prin- 
ciple of  conical  spindles  being,  however,  preserved.  The  shaft 
is  provided  with  loose  and  fast  pulley  and  coupling  lever. 

Grinding  is  executed  by  pressing  the  surfaces  to  be  ground 
against  the  face  of  the  disk,  moving  the  objects  constantly  to 
and  fro.  The  operation  requires  a  certain  manual  skill,  since, 
without  good  reason,  no  more  should  be  ground  away  on  one 
place  than  on  another.  Special  care  and  skill  are  required  for 
grinding  large  round  surfaces. 


TREATMENT   OF   METALLIC   ARTICLES.  135 

If  the  objects  are  not  to  be  treated  with  the  fine  wheel,  fine 
grinding  is  succeeded  by  brushing  with  oil  and  emery  by  means 
of  circular  brushes  formed  of  bristles  set  in  disks  of  wood  (see 
Fig.  93  )>  Genuine  bristles  being  at  -present  very  expensive, 
vegetable  fibre,  so-called  fibres,  has  been  successfully  substi- 
tuted for  them,  the  wooden  disk  being  replaced  by  an  iron  case, 
in  the  bell-shaped  cheeks  of  which  the  fibre-bundles  are  secured 

FIG.  86. 


by  means  of  strong  nuts.  Before  use  it  is  advisable  to  saturate 
the  fibre-bundles  with  oil  in  order  to  deprive  them  of  their 
brittleness,  and  thus  improve  their  lasting  quality. 

The  grinding  lathe  (Fig.  87)  is  provided  with  such  a  fibre- 
brush,  which  can,  of  course,  be  just  as  well  placed  upon  the  con- 
ical spindles  of  double  machines.  The  iron  case  is  provided  with 
a  conical  hole  corresponding  exactly  to  the  conical  spindle,  the 
large  frictional  surface  preventing  the  turning  of  the  brush  upon 
the  spindle  or  its  running  off. 

In  regard  to  grinding  the  various  metals,  the  procedure, 
according  to  the  hardness  of  the  metal,  is  as  follows : — 

Iron  and  steel  articles  are  first  ground  upon  the  roughing 
wheel,  then  fine-ground  upon  the  medium  wheel,  and  finally 
upon  the  fine  wheel,  or  brushed  with  emery  with  the  circular 


136 


ELECTRO-DEPOSITION   OF   METALS. 


brush.  Very  rough  iron  surfaces  may  first  be  ground  upon  solid 
emery  wheels  before  being  worked  upon  the  roughing  wheel. 
For  depressed  surfaces  which  cannot  be  reached  with  the 
large  emery  wheels,  small  walrus- hide  wheels  coated  with  glue 
and  emery  are  placed  upon  the  point  of  the  spindle  of  the 
polishing  lathe  (see  Fig.  95). 


FIG.  87. 


Brass  and  copper  castings  are  first  ground  upon  roughing 
wheels,  which  have  lost  part  of  their  sharpness  and  will  no 
longer  attack  iron  ;  they  are  then  ground  fine  upon  the  medium 
wheel,  and  finally  polished  upon  cloth  or  felt  disks  (bobs). 
(See  below,  under  polishing.} 

Sheets  of  brass,  German  silver,  and  copper,  as  furnished  by 
rolling-mills,  are  only  brushed  with  emery  and  then  polished 
with  Vienna  lime  or  rouge  upon  bobs. 

Zinc  castings,  as,  for  instance,  those  produced  in  lamp  fac- 
tories, are  first  thoroughly  brusjhed  by  means  of  circular 
brushes  and  emery,  and  then  polished  upon  cloth  bobs. 

Sheet  zinc  is  only  polished  with  Vienna  lime  and  ail  upon 
cloth  bobs  secured  to  the  spindle  shown  in  Fig.  95. 


TREATMENT    OF   METALLIC   ARTICLES. 


137 


FIG.  88. 


Polishing. — As  will  be  seen  from  the  foregoing,  polishing 
serves  for  making  the  articles  ready,  i.  e.,  the  final  lustre  is  im- 
parted to  them  upon  soft  polishing  disks  with  the  use  of  fine 
polishing  powders.  The  polishing  disks  or  bobs  of  fine  felt, 
shirting,  or  cloth,  are  secured  to  the  polishing  lathe,  and,  accord- 
ing to  the  hardness  of  the  metal  to  be  polished,  make  2000  to 
2500  revolutions  per  minute.  A  foot- 
lathe,  such  as  is  shown  in  Fig.  88, 
makes  generally  not  over  1800  revo- 
lutions per  minute.  Cloth  bobs  are 
made  by  placing  pieces  of  cloth  one 
upon  another  in  the  manner  described 
under  "  Nickeling  of  sheet  zinc,"  cut- 
ting out  the  centre  corresponding  to 
the  diameter  of  the  spindle,  and  secur- 
ing the  disks  of  cloth  by  means  of 
nuts  between  two  wooden  cheeks  upon 
the  spindle  of  the  polishing  lathe. 
In  place  of  cloth  bobs,  solid  round 
disks  of  felt  or  wooden  disks  covered 
with  a  layer  of  felt  may  be  used, 
especially  for  polishingsmooth  objects 

without  depressions,  the  fineness  and  softness  of  the  felt  de- 
pending on  the  degree  of  polish  to  be  imparted  and  the  hard- 
ness of  the  metal  to  be  manipulated. 

"  Compress"  polishing  wheels  made  of  leather,  felt,  canvas, 
raw  hide,  walrus,  etc.,  are  manufactured  by  the  Hanson  &  Van 
Winkle  Co.,  of  Newark,  N.  J.  The  wheel  is  shown  in  Fig  89 
and  in  sectional  view  in  Fig.  90.  The  body  of  the  wheel  is 
composed  of  a  cast-iron  hub  and  steel  side  plates  riveted  to- 
gether so  as  to  firmly  clasp  the  compress  cushion  or  cover. 
This  cushion  is  formed  of  pieces  of  leather  or  other  material 
placed  on  edge  across  the  faoe.  of  the  wheel  and  held  by  the 
shoulders  of  the  steel  side  plates,  which  fit  grooves  turned  on 
the  under  side  of  the  compressed  cushion.  This  cushion  is  one 
or  two  inches  thick,  which  gives  to  the  wheels  elasticity  and 


138 


ELECTRO-DEPOSITION   OF   METALS. 


durability.  The  special  qualities  and  advantages  over  other 
wheels  claimed  for  the  "  compress"  wheel  by  the  manufacturers 
are  as  folows : 

1.  Its  elastic  cushion  combined  with  rigid  center. 

2.  It  holds  emery  better  and  will  run   a  third  longer  at  one 
setting  up. 

3.  It  will  use  coarser  emery  and  produce  same  results. 

4.  It  cuts  faster  and  does  more  work  in  the  same  time. 


FIG.  89. 


FIG.  90. 


J 


Sectional  View. 

5.  It  is  more  easily  kept  balanced. 

6.  It  does  not  endanger  life. 

7.  It  has  several  times  the  wear  of  other  wheels. 

8.  The   cross   grain   fiber  polishing  surface   gives   a    better 
finish. 

9.  It  pays  for  itself  every  thirty  days  in  time  and  labor  saved. 

The  foot-lathe  shown  in  Fig.  91  is  designed  for  light  grind- 
ing, polishing,  and  buffing,  and  is  especially  suited  for  polishing 
silver-plate  and  silver.  It  is  constructed  of  iron  and  steel,  and 
made  very  rigid  and  strong  to  prevent  vibration.  It  stands  3 


TREATMENT   OF   METALLIC   ARTICLES. 


139 


FIG.  91. 


teet  9  inches   from  floor  to  centre  of  spindle,  has   a   26-inch 

driving-wheel  turned  with  grooves  for  three  different  speeds, 

and   will  run   the  spindle   easily  at 

from    300  to   3000  revolutions  per 

minute.     The  spindle  as  shown  in 

the  illustration  is  suitable  for  leather, 

muslin,  and  swan's-down  bobs,  buffs, 

and  mops.     This  can  be  unscrewed 

and    replaced    by  another    spindle, 

which    is    furnished    with    a   taper 

screw    for    the    bosses     of    circular 

brushes. 

Double  polishing  lathes,  accord- 
ing to  the  American  patterns  (Figs. 
92  and  93),  are  used  for  polishing 
objects  of  not  too  large  dimensions, 
while  the  lathe  shown  in  Fig.  94 
serves  chiefly  for  polishing  large 
sheets,  the  latter  being  placed  upon 
a  smooth  wooden  support  which 
rests  upon  the  knees  of  the  work- 
man, as  will  be  described  later  on  in 
speaking  of  the  nickeling  of  sheet 
zinc. 

Fig.  93  shows  a  double  polishing 
ing  lathe  of  larger  size ;  it  carries 
on  one  side  a  large  felt  disk  and  a  small  brush,  and  upon  the 
other  a  circular  brush  and  a  small  walrus-hide  buff.  The  spin- 
dle of  the  small  polishing  lathe,  Fig.  92,  carries  a  cloth  bob. 

The  lathe  (Fig.  95)  is  manufactured  by  the  Hanson  &  Van 
Winkle  Co.,  of  Newark,  N.  J.  It  is  shown  on  a  cast-iron 
pedestal,  from  which  it  can  be  disconnected  and  placed  on  a 
bench,  if  required.  It  is  made  to  run  at  a  speed  of  3000  revo- 
lutions per  minute,  at  which  speed  the  most  satisfactory  results 
are  obtained  with  muslin  buffs,  etc. 

The  lathe  is  made  with  steel  spindles,  hard-metal  bearings, 


UNIVERSITY  1 


140 


ELECTRO-DEPOSITION   OF   METALS. 


FIG.  92. 


FIG.  93. 


FIG.  94. 


TREATMENT   OF   METALLIC    ARTICLES. 


141 


and  is  designed  for  quick  speeds.  By  reason  of  the  distribution 
of  metal  it  runs  without  vibration.  It  stands  10  inches  high  to 
centre,  has  spindle  3  feet  long,  I  ^  inches  diameter,  with  collars 
on  both  ends  of  spindle.  The  pulley  is  4  inches  in  diameter,  3  J^ 
inches  face.  The  spindle  is  I  inch  in  diameter  between  collars. 

FIG.  95. 


The  lathe  is  furnished  with  fast  and  loose  pulleys  where  re- 
quired. Detachable  taper  ends  are  shown,  on  which  the  small- 
est brush  can  be  run. 

Polishing  rooms  are  not  complete  without  a  good  glue  pot. 
The  pots  used  are  often  home-made  affairs,  but  the  steam  glue 
pots  shown  in  Fig.  96  are  so  superior,  and  at  the  same  time  so 
low  in  cost,  that  it  pays  every  plater  to  have  them.  Each  pot 
sits  in  a  separate  heater.  The  heaters  are  cast-steel  chambers 
through  which  the  steam  circulates,  keeping  the  glue  at  an  even 
heat.  These  steel  chambers  also  avoid  all  escaping  steam. 
The  heaters  are  fitted  with  upright  arms  to  support  the  wheel 


1 42 


ELECTRO-DEPOSITION    OF   METALS. 


while  "  setting  up  "  with  glue.     This  allows  the  surplus  glue  to 
drop  back  into  the  glue  pot  instead  of  on  the  floor. 

The  belt  strapping  attachment  or  endless  belt  machine  shown 
in  Fig.  97  is  manufactured  by  the  Hanson  &  Van  Winkle  Co., 
of  Newark,  N.  J.  The  demand  for  machines  of  this  character 

FIG.  96. 


for  polishing  bicycle  parts  has  greatly  increased,  and  improve- 
ments have  from  time  to  time  been  made,  culminating  in  the 
present  construction,  which  is  much  more  solid  and  the  adjust- 
ment of  the  tension  of  the  belt  can  be  done  without  interfering 
with  the  operator.  There  are  fewer  parts  used  than  in  previous 
machines,  and  with  the  flanged  wheels  that  are  supplied  to  go 
on  the  pulley  lathe,  and  with  the  rubber  endless  belts  from  I  to 
3  inches  and  up  to  12  feet  in  length,  makes  this  machine  avail- 


TREATMENT   OF   METALLIC   ARTICLES. 


143 


abb  for  all  purposes.  It  is  equally  available  to  manufacturers 
of  criMlery  and  carriage  hardware,  and  on  irregularly  shaped 
articles  that  cannot  be  conveniently  polished  on  a  circular  wheel. 
No  shop  is  now  complete  without  one  or  more  flexible  shafts 
for  grinding,  polishing  and  buffing.  In  many  ways  it  will  be 
found  a  profitable  and  economical  device.  For  cleaning  and 

FIG.  97. 


grinding  heavy  castings,  for  polishing  and  buffing  all  metal  and 
glass,  it  is  a  most  indispensable  tool  where  power  is  or  can  be 
used  to  advantage.  These  shafts,  Fig.  98,  are  made  in  standard 
sizes,  from  i^-inch  diameter  core,  suitable  for  very  light  work, 
to  i^-inch  core,  capable  of  driving  a  3-inch  drill  in  iron  or 
steel. 

Fig.  99  shows  the  flexible  shaft  with  part  of  case  and  core  cut 
away  to  show  the  method  of  construction.  The  core  is  built  up 
by  laying  up  or  coiling  very  small  tempered  steel  wires  on  a  small 


144 


ELECTRO-DEPOSITION    OF   METALS. 


FIG. 


diameter,  each  successive  layer  wound  in  an  opposite  direction  of 

larger  wire,  the  ends  firmly  brazed 
together  solid.  The  fittings  are 
also  attached  by  special  brazing. 
The  coil  should  be  well  lubricated 
with  animal  oil.  Never  use  min- 
eral oil. 

Self-acting  polishing  lathes  for 
sheet-metal  will  be  discussed  un- 
der "  Nickeling  of  zinc  sheet." 

According  to  the  hardness  of 
the  material  to  be  polished,  ferric 
oxide  (colcothar  or  rouge),  trip- 
oli,  Vienna  lime,  etc.,  in  the  state 
of  an  impalpable  powder,  and 
generally  mixed  with  oil,  or 
sometimes  with  alcohol,  are  used 
as  polishing  agents.  For  hard 
metals  an  impalpable  rouge  of 
great  hardness  (No.  F  of  com- 
merce) is  employed,  for  softer 
metals  a  softer  rouge  (No.  F  F  F),  or  Vienna  lime,  tripoli,  etc. 
It  is  of  advantage  to  melt  the  rouge  with  melted  wax  and  a 
small  quantity  of  tallow,  and  cast  the  mixture  in  moulds  with 
the  aid  of  strong  pressure.  The  sticks  thus  formed  are  suffici- 
ently greasy  to  render  the  use  of  oil  superfluous.  In  order  to 
impregnate  the  surface  of  the  polishing  bob  with  the  polishing 
material,  hold  one  of  the  sticks  for  a  second  against  the  revolv- 
ing disk,  and  then  polish  the  objects  by  pressing  them  against 
the  disk,  diligently  moving  them  to  and  fro.  The  polishing  bob 
must  not  be  too  heavily  impregnated  with  rouge,  since  a  surplus 
of  the  latter  smears  instead  of  cutting  well.  In  polishing  with 
Vienna  lime,  it  is  advisable  to  moisten  the  objects  to  be  polished 
with  oil,  while  the  polishing  bobs  are  saturated  with  the  lime  by 
holding  a  piece  of  it  against  them. 

Another  process  of  polishing,  called  burnishing,  is  executed 


co-cm. 


TREATMENT   OF   METALLIC   ARTICLES. 


145 


by  means  of  tools  usually  made  of  steel  for  the  first  or  ground- 
ing process,  or  of  a  very  hard  stone,  such  as  agate  or  blood- 
stone, for  finishing.  Burnishing  is  applied  to  the  final  polishiug 
of  depositions  of  the  noble  metals. 

FIG.  99. 


2.  Mechanical  treatment  during  and  after  the  electro-plating 
process, — In  this  connection,  scratch-brushing  the  depositions 
will  be  first  considered,  the  object  of  this  operation  being,  on 
the  one  hand,  to  promote  the  regular  formation  of  certain  de- 
posits ;  and  on  the  other,  to  affect  the  physical  properties  of 
the  deposits;  and,  finally,  to  ascertain  whether  the  deposit  ad- 
heres to  the  basis-metal. 

If  it  is  seen  by  the  irregular  formation  of  the  deposit  that  the 
basis-metal  has  not  been  cleaned  with  sufficient  care  by  the  pre- 
paratory scratch-brushing,  the  object  has  to  be  taken  from  the 
bath  and  the  defective  places  again  scratch-brushed  with  the 
application  of  water  and  sand,  or  pumice-stone,  when  the  object 
is  again  pickled  and  replaced  in  the  bath. 

On  the  other  hand,  electro-deposited  metals  are  always  more 
or  less  porous,  they  having,  so  to  say,  a  net-like  structure, 
10 


146  ELECTRO-DEPOSITION   OF   METALS. 

thougfy  it  may  not  be  visible  to  the  naked  eye.  By  scratch- 
brushing  the  meshes  of  the  net  are  made  closer  by  particles  of 
metals  being  forced  into  them  by  the  brush,  and  the  deposit  is 
thus  rendered  capable  of  receiving  additional  layers  of  metal. 
Furthermore,  by  scratch-brushing  the  dead  deposits  acquire  a 
certain  lustre  which  is  enhanced  by  the  subsequent  polishing 
process.  Finally,  by  an  unsparing  application  of  the  scratch- 
brush,  it  will  best  be  seen  whether  the  union  of  the  deposit  with 
the  basis-metal  is  sufficiently  intimate  to  stand  the  subsequent 
mechanical  treatment  in  polishing  without  becoming  detached. 

According  to  the  object  in  view,  and  the  hardness  of  the  de- 
posit to  be  manipulated,  scratch-brushes  of  steel  or  brass  wire 
are  chosen.  For  nickel,  which,  as  a  rule,  requires  scratch- 
brushing  least,  and  chiefly  only  for  the  production  of  very  thick 
deposits,  steel  wire  of  0.2  millimetre  thickness  is  taken  ;  for  de- 
posits of  copper,  brass,  and  zinc,  brass  wire  of  0.2  millimetre  ;  for 
silver,  brass  wire  of  0.15  millimetre;  and  for  gold,  brass  wire  of 
0.07  to  o.i  millimetre.  Scratch- brushing  is  seldom  done  dry*; 
the  tool  as  well  as  the  pieces  should  be  constantly  kept  wet  with 
liquids,  especially  such  as  produce  a  lather  in  brushing,  for 
instance,  water  and  vinegar,  or  sour  wine,  or  solutions  of  cream 
of  tartar  or  alum,  when  it  is  desired  to  brighten  a  gold  deposit 
which  is  too  dark ;  but  that  most  generally  used  is  a  decoction 
of  licorice-root,  of  horse-chestnut,  of  marshmallow,  of  soap- 
wort,  or  of  the  bark  of  Panama-wood,  all  of  which,  being 
slightly  mucilaginous,  allow  of  a  gentle  scouring  with  the 
scratch-brush,  with  the  production  of  an  abundant  lather.  A 
good  adjunct  for  scratch-brushing  is  a  shallow  wooden  tub  con- 
taining the  liquid  employed,  with  a  board  laid  across  it  nearly 
level  with  the  edges,  which,  however,  project  a  little  above. 
This  board  serves  as  a  rest  for  the  pieces. 

The  hand  scratch-brush,  when  operating  upon  small  objects, 
is  held  by  the  workman  in  the  same  manner  as  a  paint  brush, 
and  is  moved  over  the  object  with  a  back  and  forward  motion 
imparted  by  the  wrist  only,  the  forearm  resting  on  the  edge  of 
the  tub.  For  larger  objects,  the  workman  holds  his  extended 


TREATMENT    OF   METALLIC    ARTICLES. 


147 


fingers  close  to  the  lower  part  of  the  scratch  brush,  so  as  to 
give  the  wires  a  certain  support,  and,  with  raised  elbow,  'strikes 
the  pieces  repeatedly,  at  the  same  time  giving  the  tool  a  sliding 
motion.  When  a  hollow  is  met  with,  which  cannot  be  scoured 
longitudinally,  a  twisting  motion  is  imparted  to  the  tool. 

FIG.  100. 


The  lathe  brush  (Fig.  TOO)  is  mounted  upon  a  spindle,  and  is 
provided  above  with  a  small  reservoir  to  contain  the  lubricating 
fluid,  a  small  pipe  with  a  tap  serving  to  conduct  the  solution 
from  this  to  a  point  immediately  above  the  revolving  brush. 
The  top  of  the  brush  revolves  towards  the  operator,  who 
presents  the  object  to  be  scratch-brushed  to  the  bottom.  The 
brush  is  surrounded  by  a  wooden  cage  or  screen  to  prevent 
splashing.  To  protect  the  operator  against  the  water  projected 


148  ELECTRO-DEPOSITION   OF   METALS. 

by  the  rapid  motion,  there  is  fixed  to  the  top  of  the  frame  a 
small  inclined  board,  which  reaches  a  little  lower  than  the  axis 
of  the  brush  without  touching  it.  This  board  receives  the  pro- 
jected liquid,  and  lets  it  fall  into  a  zinc  trough,  which  forms  the 
bottom  of  the  box.  Through  an  outlet  provided  in  one  of  the 
angles  of  the  trough  a  gum  tube  conveys  the  waste  liquid  to  a 
reservoir  below.  After  scratch- brushing  every  trace  of  the 
lubricating  liquid  must  be  washed  away  before  placing  or  re- 
placing the  objects  in  the  bath. 

The  finished  electro-plated  objects  are  first  rinsed  in  clean 
water  to  remove  the  solution  constituting  the  bath  adhering  to 
them ;  they  are  next  immersed  in  hot  water,  where  they  re- 
main until  they  have  acquired  the  temperature  of  the  water,  and 
are  then  quickly  rubbed  with  dry,  hot  sawdust.  It  is  best  to 
use  sawdust  of  soft  wood,  free  from  tannin,  such  as  maple, 
poplar,  or  pine ;  oak  sawdust  is  not  suitable  for  the  purpose  on 
account  of  its  content  of  tannin,  which  imparts  a  dirty  color- 
ation to  the  electro-deposits.  Boxwood  sawdust,  though  much 
used,  is  not  sufficiently  absorbent,  and  sticks  to  the  moist 
objects.  The  sawdust  used  must  be  freed  from  coarser  parti- 
cles of  wood  by  sifting.  For  holding  the  sawdust  a  zinc  box 
with  double  bottom  is  frequently  used,  which  is  heated  by  waste 
steam  or  some  other  process.  In  order  to  remove  all  moisture 
from  the  pores  it  is  advisable  to  place  plated  objects  of  iron  and 
steel  for  a  few  hours  in  an  oven  heated  to  between  140°  and 
175°  F.  A  very  good  method  of  freeing  nickeled  objects  from 
all  moisture  which  may  have  collected  in  the  pores  is  to  im- 
merse them  for  about  ten  minutes  in  boiling  linseed  oil,  and, 
after  allowing  them  to  drain  off,  to  remove  the  adhering  oil  by 
rubbing  with  sawdust..  According  to  some  electro-platers,  the 
deposit  of  nickel  thus  treated  loses  its  brittleness  and  will  stand 
bending  several  times,  for  instance,  wire,  sheets,  etc.,  without 
breaking.  Experiments  made  by  Dr.  George  Langbein  did  not 
confirm  these  statements,  but  the  security  against  rust  of  the 
nickeled  iron  objects  is  found  to  be  considerably  enhanced  by 
boiling  in  linseed  oil. 


TREATMENT   OF   METALLIC   ARTICLES.  149 

The  electro-plated  objects,  when  dry,  are  finely  polished, 
which  is  effected  upon  polishing  bobs  of  fine  felt,  cloth,  or 
flannel,  with  the  use  of  fine  rouge,  Vienna  lime,  tripoli,  etc.,  or 
by  burnishing. 

Nickel  deposits  are  almost  without  exception  polished  upon 
cloth  or  felt  bobs  with  rouge  or  Vienna  lime  and  oil.  Copper 
and  brass  deposits  are  polished  with  fine  flannel  bobs,  the  polish- 
ing powder  being  applied  very  sparingly.  Deposits  of  tin  are 
generally  only  scratch-brushed,  it  being  impossible  to  impart 
great  lustre  to  this  metal  by  polishing  with  bobs :  after  drying, 
the  deposit  is  polished  with  whiting.  Deposits  of  gold  and  silver 
as  well  as  of  platinum  are  polished  by  burnishing,  the  steel 
burnisher  being  used  for  the  grounding  process,  and  an  agate 
or  bloodstone  burnisher  for  finishing.  The  operation  of  burn- 
ishing is  carried  on  as  follows :  Keep  the  tool  continually 
moistened  with  soap-suds.  Take  hold  of  the  tool  very  near  to 
the  end,  and  lean  very  hard  with  it  on  those  parts  which  are  to 
be  burnished,  causing  it  to  glide  by  a  backward  and  forward 
motion  without  taking  it  off  the  piece.  When  it  is  requisite 
that  the  hand  should  pass  over  a  large  surface  at  once  without 
losing  its  point  of  support  on  the  work  bench,  be  careful  in  tak- 
ing hold  of  the  burnisher  to  place  it  just  underneath  the  little 
finger.  By  these  means  the  work  is  done  more  quickly,  and 
the  tool  is  more  solidly  fixed  in  the  hand.  The  burnishers  are 
of  various  shapes  to  suit  the  requirements  of  different  kinds  of 
work,  the  first  rough  burnishing  being  often  done  by  instru- 
ments with  comparatively  sharp  edges,  while  the  finishing  oper- 
ations are  accomplished  with  rounded  ones.  Fig.  101  illustrates 
the  most  common  forms  of  burnishers  of  steel  and  agate.  Both 
must  be  free  from  cracks  and  highly  polished.  To  keep  them 
free  from  blemishes  they  are  from  time  to  time  polished  by 
vigorously  rubbing  them  with  fine  tin  putty,  rouge  or  calcined 
alum  upon  a  strip  of  leather  fastened  upon  a  piece  of  wood 
which  is  placed  in  a  convenient  position  upon  the  work  bench. 

The  objects  polished  with  Vienna  lime  and  oil,  or  with  rouge, 
have  to  be  freed  from  adhering  polishing  dirt,  which,  with  flat 


I5O  ELECTRO-DEPOSITION   OF   METALS. 

smooth  objects,  is  effected  by  wiping  with  a  flannel  rag  and 
Vienna  lime,  and  in  those  with  depressions  or  dead  surfaces  by 
brushing  with  a  soft  brush  and  soap-water,  and  then  drying  in 
sawdust. 

FIG.  101. 


*   B.   Chemical  Treatment. 

While'the  preparation  of  a  pure  metallic  and,  at  the  same 
time,  smoother  surface  is  the  aim  of  the  mechanical  treatment, 
the  chemical  preparation  of  the  objects  serves,  on  the  one  hand, 
the  purpose  of  facilitating  the  mechanical  treatment  by  soften- 
ing and  dissolving  the  impure  surface,  and,  on  the  other,  of 
freeing  the  mechanically  prepared  objects  from  adhering  oil, 
grease,  dirt,  etc.,  so  as  to  bring  them  into  the  state  of  absolute 
purity  required  for  the  electro-plating  process. 

Pickling. — The  composition  of  the  pickling  fluid  varies 
according  to  the  nature  of  the  metal  which  is  to  be  pickled. 

Cast-iron  and  wrought-iron  objects  are  pickled  in  a  mixture  of 


TREATMENT   OF   METALLIC   ARTICLES.  !$! 

1  part  by  weight  of  sulphuric  acid  of  66°  Be.  and  15  of  water; 
hydrochloric  acid  may  be  substituted  for  the  sulphuric  acid. 

An  excellent  pickle  for  iron  is  obtained  by  mixing  10  quarts 
of  water  with  28  ozs.  of  concentrated  sulphuric  acid,*  dissolving 

2  ozs.  of  zinc  in  the  mixture  and  adding  12  ozs.  of  nitric  acid. 
This  mixture  makes  the  iron  objects  bright,  while  they  become 
black   in   dilute   sulphuric   or  hydrochloric   acid.     To   cleanse 
badly  rusted  iron  objects  without  attacking  the  iron  itself,  it  is 
recommended  to  pickle  them   in   a   concentrated   solution   of 
chloride  of  tin,  which,  however,  should  not  contain   too  much 
free  acid,  as  otherwise  the  iron  is  attacked. 

The  duration  of  pickling  depends  on  the  more  or  less  thick 
layer  of  scale,  etc.,  which  is  to  be  removed  or  softened ;  the 
process  may  be  considerably  assisted  and  the  time  shortened  by 
frequent  scouring  with  sand  or  pumice.  The  pickled  articles 
are  rinsed  in  cold  water,  then  immersed  in  hot  water,  and  dried 
in  sawdust.  In  order  to  neutralize  the  acid  remaining  in  the 
pores,  it  is  advisable  to  make  the  rinsing  water  alkaline  by  the 
addition  of  caustic  potash  or  soda,  etc. 

Zinc  objects  are  only  pickled  when  they  show  a  thick  layer 
of  oxide,  in  which  case  pickling  is  also  effected  in  dilute  sul- 
phuric or  hydrochloric  acid,  and  brushing  with  fine  pumice.  A 
very  useful  pickle  for  zinc  consists  of  sulphuric  acid  100  parts 
by  weight,  nitric  acid  100,  and  common  salt  I.  The  zinc  objects 
are  immersed  in  the  mixture  for  one  second,  and  then  quickly 
rinsed  off  in  water  which  should  be  frequently  changed. 

Copper,  and  its  alloys  brass,  bronze,  tombac,  and  German  silver, 
are  cleaned  and  brightened  by  dipping  in  a  mixture  of  nitric 
acid,  sulphuric  acid,  and  lampblack,  a  suitable  pickle  consisting 
of  sulphuric  acid,  of  66°  Be.,  50  parts  by  weight,  nitric  acid,  of 
36°  Be.,  i oo,  common  salt  I,  and  lampblack  I.  In  order  to 
remove  the  brown  coating,  due  to  cuprous  oxide,  the  objects 
are  first  pickled  in  dilute  sulphuric  acid,  and  then  dipped  for  a 
few  seconds,  with  constant  agitation,  in  the  above-mentioned 

*  The  acid  should  be  poured  into  the  water,  and  not  the  water  into  the  acid. 


152  ELECTRO-DEPOSITION   OF   METALS. 

pickle  until  they  show  a  bright  appearance.  They  are  then 
immediately  rinsed  in  water  to  check  any  further  action  of  the 
pickle. 

If  objects  of  copper  or  its  alloys  are  not  to  be  subjected,  after 
pickling,  to  further  mechanical  treatment,  or  are  to  be  at  once 
placed  in  the  electro-plating  bath,  it  is  best  to  execute  the  pick- 
ling process  in  two  operations  by  treating  them  in  a  preliminary 
pickle  and  brightening  them  in  the  bright- dipping  bath.  The 
preliminary  pickle  consists  of  nitric  acid,  of  36°  Be.,  200  parts 
by  weight,  common  salt  i,  lampblack  2.  In  this  preliminary 
pickle  the  articles  are  allowed  to  remain  until  all  impurities  are 
removed,  when  they  are  rinsed  in  a  large  volume  of  water, 
dipped  in  boiling  water,  so  that  they  quickly  dry,  and  plunged 
into  the  bright-dipping  bath,  which  consists  of  nitric  acid,  of  40° 
Be.,  75  parts  by  weight,  sulphuric  acid,  of  60°  Be.,  100,  and 
common  salt  I.  It  is  not  advisable  to  bring  the  objects  which 
have  passed  through  the  preliminary  pickle  and  rinsing  water 
directly,  while  still  moist,  into  the  bright-dipping  bath,  since  for 
the  production  of  a  beautiful  pure  lustre  the  introduction  of 
water  into  the  bright-dipping  bath  must  be  absolutely  avoided. 

Hence  the  objects  treated  in  the  preliminary  pickle  should 
first  be  dried  by  heating  in  hot  water,  shaking  the  latter  off. 

Potassium  cyanide,  dissolved  in  ten  times  its  weight  of  water, 
is  often  used  instead  of  the  acid  pickle  for  brass,  especially  when 
it  is  essential  that  the  original  polish  upon  the  objects  should 
not  be  destroyed,  as  in  the  preparation  of  articles  for  nickel- 
plating.  The  objects  should  remain  in  this  liquid  longer  than 
in  the  acid  pickle,  because  the  metallic  oxides  are  far  less 
soluble  in  this  than  in  the  latter.  In  all  cases  the  final  cleaning 
in  water  must  be  observed. 

All  acid  pickles  used  for  different  kinds  of  work  should  be 
kept  distinct  from  each  other,  so  that  one  metal  may  not  be 
dipped  into  a  solution  containing  a  more  electro-negative  metal, 
which  would  deposit  upon  it  by  a  chemical  exchange. 

The  pickled  objects  must  not  be  unnecessarily  exposed  to  the 
air,  and  should  be  transferred  as  quickly  as  possible  from  the 


TREATMENT   OF   METALLIC   ARTICLES.  153 

pickle  to  the  wash-waters,  and  then  to  the  electro-plating  bath, 
or,  if  this  is  not  feasible,  kept  under  pure  water.  Pickled  ob- 
jects which  are  not  to  be  plated  are  carefully  washed  in 
water,  which  should  be  frequently  changed,  rinsed,  drawn 
through  a  solution  of  tartar,  and  dried  by  dipping  in  hot  water 
and  rubbing  with  saw-dust. 

Places  soldered  with  soft  solder,  as  well  as  parts  of  iron,  be- 
come black  by  pickling,  and  have  to  be  brightened  by  scouring 
with  pumice,  or  by  scratch-brushing. 

It  is  frequently  required  that  bright  objects  of  brass  or  other 
alloy  of  copper  should  be  given  a  dead  or  dull  surface  by  pick- 
ling, so  that  after  plating  they  show  a  beautiful  dead  lustre. 
This  may  be  effected  in  various  ways.  Every  bright-dipping 
bath  acts  as  a  dead  dip  if  the  articles  are  allowed  to  remain  in 
it  for  a  longer  time  and  at  a  higher  temperature.  A  better  ef- 
fect is,  however,  produced  by  adding  zinc  sulphate  (white 
vitriol)  to  the  pickle,  the  deadening  being  the  stronger  the 
more  zinc  sulphate  is  added.  A  good  dead  dip  is  prepared  by 
adding  a  solution  of  0.35  oz.  of  zinc  sulphate  in  3^  ozs.  of 
water  to  the  cold  mixture  of  6j^  Ibs.  of  nitric  acid,  of  36°  Be., 
4.4  Ibs.  of  sulphuric  acid,  of  66°  Be.,  and  J^  oz.  of  common 
salt.  According  to  the  shade  desired,  the  articles  are  left  in  this 
mixture  for  2  to  10  minutes,  and  as  they  come  from  it  with  a 
faded  earthy  appearance,  they  are  plunged  momentarily  into  a 
bright-dipping  bath,  whereby  they  acquire  a  dead  lustre,  and 
are  then  quickly  rinsed  in  a  large  volume  of  clean  water. 

Generally  speaking,  it  may  be  said  that  less  depends  on  the 
composition  of  the  pickle  than  on  quick  and  .skillful  manipula- 
tion;  and  as  good  results  have  always  been  obtained  with  the 
above-mentioned  mixture,  there  is  no  reason  for  repeating  the 
innumerable  receipts  given  for  pickles.  The  main  points  are  to 
have  the  acid  mixture  as  free  from  water  as  possible,  further 
to  develop  hyponitric  acid,  which  is  effected  by  the  reduc- 
tion of  nitric  acid  in  consequence  of  the  addition  of  organic  sub- 
stances (lampblack,  sawdust,  etc.),  and  of  chlorine,  which  is 
formed  by  the  action  of  the  sulphuric  acid  upon  the  common 


154  ELECTRO-DEPOSITION   OF   METALS. 

salt.  The  volume  of  the  dipping  bath  should  not  be  too  small, 
since  in  pickling  the  acid  mixture  becomes  heated  and  the  in- 
creased temperature  shows  a  very  rapid,  frequently  not  con- 
trollable, action,  so  that  a  corrosion  of  small  articles  may 
readily  take  pface.  It  is  therefore  necessary  to  allow  the  acid 
mixture,  after  its  preparation,  to  thoroughly  cool  off;  pour  the 
sulphuric  acid  into  the  nitric  acid  (never  the  reverse!!},  and 
allow  the  mixture,  which  thereby  becomes  strongly  heated,  to 
cool  off  to  at  least  the  ordinary  temperature. 

In  order  to  be  sure  of  the  uniform  action  of  the  pickle  upon 
all  parts,  it  is,  in  all  cases,  advisable  previous  to  pickling  to  free 
the  articles  from  grease  by  one  of  the  methods  given  later  on. 

In  pickling  abundant  vapors  are  evolved  which  have  an  in- 
jurious effect  upon  the  health  of  the  workmen,  and  corrode 
metallic  articles  exposed  to  them.  The  operation  should,  there- 
fore be  conducted  in  the  open  air,  or  under  a  well-drawing 
vapor  flue. 

In  large  establishments  it  may  happen  that  the  quantity  of 
escaping  acid  vapors  is  so  large  as  to  become  a  nuisance  to  the 
neighborhood,  which  the  proprietors  may  be  ordered  by  the 
authorities  to  abate.  The  evil  is  best  remedied  by  a  small  ab- 
sorbing plant,  as  follows:  — 

Connect  the  highest  point  of  the  vapor  flue  D  (Fig.  102) 
by  a  wide  clay  pipe  R  with  a  brick  reservoir,  A,  laid  in  cement, 
so  that  R  enters  A  a  few  centimeters  above  the  level  of  the  fluid, 
kept  at  the  same  height  by  the  discharge  pipe  b.  Above,  the 
reservoir  is  closed  by  a  vault  through  which  the  water  conduit 
W  is  introduced.  Below  the  sieve  5,  which  is  made  of  wood  and 
coated  with  lacquer,  a  wide  clay  pipe  R^  leads  to  the  chimney  of 
the  steam  boiler ;  or  the  suction  pipe  of  an  injector  is  introduced 
in  this  place,  in  which  the  air  from  the  vapor  flue  is  sucked 
through  the  reservoir  and  allowed  to  escape  into  the  open  air  or 
into  a  chimney.  Through  the  man-hole  M  the  sieve-bottom  5 
of  the  reservoir  is  filled  with  large  pieces  of  chalk  or  limestone, 
the  manner  of  operating  being  then  as  follows :  A  thin  jet  of 
water  falls  upon  5,  where  it  is  distributed  and  runs  over  the 


TREATMENT   OF   METALLIC    ARTICLES. 


155 


layer  of  chalk.  The  air  of  the  pickling  room  saturated  with 
acid  vapor  moves  upward  in  consequence  of  the  draught  of  the 
chimney  of  the  steam  boiler,  the  injector  or  the  ventilator,  and 
yields  its  content  of  acid  to  the  layer  of  chalk,  while  the  neutral 
solution  of  calcium  nitrate  and  calcium  chloride,  which  has 
been  formed,  runs  off  through  b. 


FIG.  102. 


The  absorption  of  the  acid  vapors  may,  of  course,  be  effected 
by  apparatus  of  different  construction,  but  the  one  above  de- 
scribed may  be  recommended  as  being  simple,  cheap,  and 
effective. 

The  considerable  consumption  of  acid  for  pickling  purposes 
in  large  establishments  makes  it  desirable  to  regain  the  acid 
and  metal  contained  in  the  exhausted  dipping  baths.  The 
following  process  has  proved  very  successful  for  this  purpose : 
Mix  the  old  dipping  baths  with  ^  their  volume  of  concentrated 
sulphuric  acid,  and  bring  the  mixture  into  a  nitric  acid  distill- 
ing apparatus.  Distil  the  nitric  acid  off  at  a  moderate  temper- 
ature, condense  it  in  cooled  clay-coils,  and  collect  it  in  glass 


156  ELECTRO-DEPOSITION   OF   METALS. 

balloons.  To  the  residue  in  the  still  add  water,  precipitate 
from  the  blue  solution,  which  contains  sulphate  of  copper  and 
zinc,  the  copper  with  zinc  waste,  and  add  zinc  until  evolution 
of  hydrogen  no  longer  takes  place.  Filter  off  the  precipitated 
copper  through  a  linen  bag,  wash  and  dry.  The  fluid  running 
off,  which  contains  zinc  sulphate,  is  evaporated  to  crystallization 
and  yields  quite  pure  zinc  sulphate,  which  may  be  sold  to  dye- 
works,  or  for  the  manufacture  of  zinc-white. 

According  to  local  conditions,  for  instance,  if  the  zinc  sul- 
phate cannot  be  profitably  sold  in  the  neighborhood,  or  zinc 
waste  cannot  be  obtained,  it  may  be  more  advantageous  to  omit 
the  regaining  of  zinc  from  the  dipping  baths.  In  this  case,  the 
fluid  which  is  obtained  by  mixing  the  contents  of  the  still  with 
water  is  compounded  with  milk  of  lime  until  it  shows  a  slightly 
acid  reaction.  The  gypsum  formed  is  allowed  to  settle,  and 
after  bringing  the  supernatant  clear  fluid  into  another  reservoir 
the  copper  is  precipitated  by  the  introduction  of  old  iron.  The 
first  rinsing  waters  in  which  the  pickled  objects  are  washed  are 
treated  in  the  same  manner.  The  precipitated  copper  is  washed 
and  dried. 

For  the  production  of  a  grained  surface  by  pickling  a  mix- 
ture of  i  volume  of  saturated  solution  of  bichromate  of  potash 
in  water  and  2  volumes  of  concentrated  hydrochloric  acid  may 
be  recommended.  The  brass  articles  are  allowed  to  remain  in 
the  mixture  for  several  hours,  when  they  are  momentarily 
plunged  into  the  bright-dipping  bath,  and  rinsed  in  a  large 
volume  of  water,  which  should  be  frequently  changed. 

Removal  of  grease. — This  operation  is  to  be  executed  with 
the  greatest  nicety,  because  on  it  chiefly  depends  the  success 
of  electro-plating.  Its  object  is  to  remove  every  trace  of  im- 
purity, be  it  due  to  touching  with  the  hands  or  to  the  manipu- 
lation in  grinding  and  polishing. 

According  to  the  preparatory  treatment  of  the  objects,  the 
removal  of  grease  is  a  more  or  less  complicated  operation. 
Large  amounts  of  oily  or  greasy  matter  should  be  removed  by 
rinsing  in  benzine,  it  being  recommended  to  execute  this  opera- 


TREATMENT   OF   METALLIC   ARTICLES.  157 

tion  immediately  after  grinding  and  polishing,  so  that  the  oil 
used  in  these  operations  has  no  chance  of  hardening  as  is  fre- 
quently the  case  with  objects  polished  with  Vienna  lime  and  oil. 
Instead  of  cleaning  with  benzine,  the  objects,  as  far  as  their 
nature  allows,  may  be  boiled  in  a  hot  lye  of  I  part  of  caustic 
potash  or  soda  in  10  of  water,  until  all  the  grease  is  saponified, 
when  the  dirt,  consisting  of  grinding  powder,  can  be  readily  re- 
moved by  brushing.  In  place  of  solutions  of  caustic  alkalies, 
hot  solutions  of  potash  or  soda  may  be  used,  but  their  action 
is  much  slower  and  offers  no  advantages.  Objects  of  tin,  lead, 
and  Britannia,  being  attacked  by  the  hot  lye,  must  be  left  in 
contact  with  it  for  a  short  time  only. 

The  articles  thus  freed  from  the  larger  portion  of  grease  are 
first  rinsed  in  water,  and  then  for  the  removal  of  the  last  traces 
of  grease  brushed  with  a  bristle  brush  and  a  mixture  of  water, 
quick-lime,  and  whiting,  until  when  rinsing  in  water  all  por- 
tions appear  equally  moistened  and  no  dry  places  are  visible. 

The  lime  mixture  is  prepared  by  slaking  freshly  burnt  lime, 
free  from  sand,  with  water  to  an  impalpable  powder,  mixing 
i  part  of  this  with  I  of  fine  whiting,  and  adding  water  with 
constant  stirring  until  a  paste  of  the  consistency  of  syrup  is 
formed. 

The  shape  of  many  objects  presents  certain  difficulties  in 
the  removal  of  grease ;  the  deeper  portions  cannot  be  reached 
with  the  brush,  as,  for  instance,  in  skates,  which  often  are  to 
be  nickeled  in  a  finished  state.  In  this  case  the  objects  are 
drawn  in  succession  through  three  different  benzine  vessels ;  in 
the  first  benzine  most  of  the  grease  is  dissolved,  the  rest  in  the 
second,  while  the  third  serves  for  rinsing  off.  When  the  ben- 
zine in  the  first  vessel  contains  too  much  grease,  it  is  emptied 
and  filled  with  fresh  benzine,  and  then  serves  as  the  third  vessel, 
while  that  which  was  formerly  the  second  becomes  the  first, 
and  the  third  the  second.  After  rinsing  in  the  third  benzine 
vessel,  the  objects  are  plunged  in  hot  water,  then  for  a  few 
seconds  dipped  in  thin  milk  of  lime,  and  finally  thoroughly 
rinsed  in  water.  It  is  recommended  not  to  omit  the  treatment 
with  milk  of  lime  of  objects  freed  from  grease  with  benzine. 


I58 


ELECTRO-DEPOSITION    OF   METALS. 


To  avoid  subsequent  touching  with  the  hands  the  objects, 
before  freeing  them  from  grease,  must  of  course  -be  tied  to  the 
metallic  wires  (of  soft  copper)  by  which  they  are  suspended  in 
the  electro-plating  bath.  In  removing  the  grease  by  the  wet 
method  a  layer  of  oxide  scarcely  perceptible  to  the  eye  is 
frequently  formed  upon  the  metals.  This  layer  of  oxide  has  to 
be  removed,  the  liquid  used  for  the  purpose  varying,  of  course, 
with  the  nature  of  the  layer. 

Objects  of  iron  and  steel  as  well  as  of  zinc  are  momentarily 
plunged  in  a  mixture  of  sulphuric  acid  I  part  by  weight  and 
water  20  parts,  and  quickly  rinsed  off  in  clean  water.  Highly 
polished  objects  of  iron  and  steel,  after  being  treated  with  this 
mixture,  are  best  again  rapidly  brushed  with  lime  paste,  and, 
after  rinsing  off  quickly,  immediately  brought  into  the  electro- 
plating bath. 

FIG.  103. 


Copper p,  brass,  bronze,  German  silver,  and  tombac  are  best 
treated  with  a  dilute  solution  of  potassium  cyanide,  I  part  of  60 
per  cent,  potassium  cyanide  in  1 5  to  20  of  water.  The  objects 
are  then  quickly  rinsed  off  and  placed  in  the  electro-plating 
bath. 

Lead  and  Britannia  may  be  treated  with  water  slightly  acidu- 
lated with  nitric  acid. 

The  steel  spring  carboy  rocker  shown  in  Fig.  103  overcomes  the 


PROCESSES    OF   ELECTRO-DEPOSITION.  159 

difficult  and  dangerous  operation  of  tilting  heavy  carboys  con- 
taining acids.  It  is  the  acme  of  convenience  and  simplicity. 
It  empties  the  carboy  with  ease,  saves  waste  of  contents  and 
time  in  handling,  and  prevents  danger  to  the  person  and  cloth- 
ing of  the  operator.  It  is  very  strong,  and  can  be  hung  up  out 
of  the  way  when  not  in  use. 


CHAPTER  VI. 

PROCESSES   OF    ELECTRO-DEPOSITION. 

NEXT  to  the  proper  mechanical  and  chemical  preparations  of 
the  objects,  the  success  of  the  process  of  electro-deposition  de- 
pends on  the  suitable  composition  of  the  electrolytic  solutions 
(baths),  and  the  current-strength  which  is  conducted  into  the 
bath  for  the  precipitation  of  the  metals.  In  regard  to  the  latter 
the  most  essential  conditions  have  already  been  discussed  in 
Chap.  IV.,  "Electro-plating  Plants  in  General,"  and  will  be 
further  referred  to  in  speaking  of  the  several  electro-plating 
processes.  Hence,  the  general  rules  which  have  to  be  observed 
in  the  preparation  of  the  baths  will  first  be  considered. 

Water  being  the  solvent  for  all  electrolytic  baths,  its  constitu- 
tion is  by  no  means  of  such  slight  importance  as  is  frequently 
supposed. 

Spring  and  well  water  often  contain  considerable  quantities  of 
lime,  magnesia,  common  salt,  iron,  etc.,  the  presence  of  which  may 
cause  various  kinds  of  separations  in  the  baths ;  on  the  other 
hand,  river  water  is  frequently  impregnated  to  such  an  extent 
with  organic  substances  that  its  employment  without  previous 
purification  cannot  be  recommended.  No  doubt,  distilled 
water,  or  in  want  of  that  rain  water,  is  the  most  suitable  for  the 
preparation  of  baths.  However,  rain  water  collected  from 
metal  roofs  should  not  be  used,  nor  that  running  off  from  other 
roofs,  it  being  contaminated  with  dust.  Rain  water  should  be 


l6o  ELECTRO-DEPOSITION   OF   METALS. 

caught  in  vessels  of  glass,  earthenware,  or  wood,  free  from 
tannin,  and  filtered.  Where  river  or  well  water  has  to  be  em- 
ployed, thorough  boiling  and  filtering  before  use  are  abso- 
lutely necessary  in  order  to  separate  the  carbonates  of  the 
alkaline  earths  held  in  solution.  By  boiling,  a  possible  con- 
tent of  sulphuretted  hydrogen  is  also  driven  off. 

Another  important  factor  is  the  purity  of  the  chemicals  used 
for  the  baths,  the  premature  failure  of  the  latter  being  in  most 
cases  caused  by  the  unsuitable  nature  of  the  chemicals,  which 
also  frequently  gives  rise  to  abnormal  phenomena  inexplicable 
to  the  operator.  Chloride  of  zinc,  for  instance,  may  serve  as 
an  example.  It  is  found  in  commerce  in  very  varying  quali- 
ties, it  being  prepared  for  dyeing  purposes  with  about  70  per 
cent,  actual  content  of  chloride  of  zinc,  for  pharmaceutical  pur- 
poses with  about  90  per  cent.,  and  for  electro-plating  purposes 
with  98  or  99  per  cent.  Now  it  will  readily  be  seen  that  if  an 
operator  who  is  preparing  a  brass  bath  according  to  a  formula 
which  calls  for  pure  chloride  of  zinc  uses  a  preparation  in- 
tended for  dyeing  purposes,  there  will  be  a  deficiency  of 
metallic  zinc  in  the  bath,  and  the  content  of  copper  in  the 
bath  being  too  large  in  proportion  to  the  zinc  present,  will 
cause  reddish  shades  in  the  deposits. 

Likewise,  in  case  the  operator  uses  potassium  cyanide  of 
low  content,  when  the  formula  calls  for  a  pure  article  with  98 
per  cent.,  he  will  not  be  able  to  effect  the  solution  of  copper 
or  zinc  salts  with  the  quantity  prescribed.  Furthermore, 
potassium  cyanide,  in  the  preparation  of  which  prussiate  of 
potash  containing  potassium  sulphate  is  used,  will  cause,  by 
reason  of  the  formation  of  potassium  sulpho-cyanide,  various 
disturbing  influences  (formation  of  bubbles  in  the  deposit), 
the  explanation  of  which  is  difficult  to  the  operator,  who, 
trusting  to  the  purity  of  the  chemicals,  seeks  elsewhere  for  the 
causes  of  the  abnormal  phenomena. 

Sodium  sulphite  may  in  a  similar  manner  cause  great  annoy- 
ance if  the  suitable  preparation  is  not  used.  There  is  a  crystal- 
lized neutral  salt  which  is  employed  for  many  gold-baths,  and 


PROCESSES    OF   ELECTRO-DEPOSITION.  l6l 

also  the  sodium  bisulphite  in  the  form  of  powder  which  serves 
for  the  preparation  of  copper  and  brass  baths.  If  the  latter 
should  be  used  in  the  preparation  of  gold  baths,  the  gold 
would  be  reduced  from  the  solution  of  its  salts  and  precipitated 
as  a  brown  powder. 

Or,  if  in  preparing  nickel  baths  a  salt  containing  copper  is 
used,  the  nickeling  will  never  be  of  a  pure  white  color,  but 
show  shades  having  not  even  a  distant  resemblance  to  the  color 
of  nickel. 

The  above-mentioned  examples  suffice  to  show  how  careful 
the  operator  must  be  in  the  selection  of  the  sources  from  which 
he  obtains  his  supplies.  It  may  here  be  mentioned  that  all  the 
directions  given  in  the  following  pages  refer  to  chemically  pure 
products  ;  where  products  of  a  lower  standard  may  be  used  the 
content  is  especially  given. 

For  the  concentration  of  the  various  baths,  no  general  rules 
can  be  laid  down ;  neither  can  the  determination  of  the  density 
of  the  baths  by  the  hydrometer  be  relied  on.  If  the  electro- 
plating solutions  consisted  of  nothing  but  the  pure  metallic 
salts,  the  specific  gravity,  which  is  indicated  by  the  hydrometer- 
degrees  might  serve  for  an  estimation  of  their  value.  But  such 
an  estimation  is  often  apt  to  prove  deceptive,  since  to  decrease 
the  resistance  the  baths  also  require  conducting  salts,  and  by 
the  addition  of  a  larger  quantity  of  them  the  specific  gravity  of 
a  bath  may  be  increased  to  any  extent  without  the  content  of 
the  more  valuable  metal  being  greater  than  in  a  bath  showing 
fewer  hydrometer-degrees. 

If  the  composition  of  a  correct  bath  when  freshly  prepared 
is  known,  as  well  as  its  gravity  in  degrees  Baume,  conclusions 
as  to  the  condition  of  the  bath  may  be  drawn  from  changes  in 
the  specific  gravity.  All  baths,  with  the  exception  of  gold 
baths,  measure  between  6°  and  10°  Baume.  If  now  a  nickel 
bath  after  its  preparation  shows  the  standard  gravity — 7°  Be 
— for  nickel  baths  and  it  shows  later  on  9°,  the  greater  gravity 
is  either  due  to  evaporation  of  water  or  to  excessive  freshening 
or  strengthening  of  the  bath.  Such  a  bath  generally  yields 
ii 


1 62  ELECTRO-DEPOSITION   OF   METALS. 

dark  and  spotted  nickeling,  the  deposit  is  formed  in  a  sluggish 
manner,  and  the  operator  may  then  learn  from  the  hydrometer 
that  the  cause  of  these  phenomena  is  not  due  to  a  contamina- 
tion of  the  bath,  but  to  its  over-concentration.  Baths  too  con- 
centrated readily  deposit  salt  in  crystals  on  the  anodes  and  on 
the  sides  of  the  vats,  which  should  by  no  means  take  placts,  and 
there  is  even  danger  that  microscopic  crystals  may  deposit 
upon  the  articles  and  cause  holes  in  the  deposit. 

An  electrolytic  bath  should  not  be  poor  in  metal,  as  otherwise 
it  soon  becomes  exhausted,  and  besides  the  deposits  form  more 
slowly  than  in  a  bath  with  a  correct  content  of  metal;  on  the 
other  hand,  the  bath  must  not  be  too  concentrated,  as,  in  this 
case,  salts  in  the  form  of  crystals  readily  separate  and  deposit 
themselves  upon  the  anodes,  the  sides  of  the  vessels,  and  even 
upon  the  articles  themselves,  which  may  cause  holes  to  form  in 
the  deposit ;  or  the  crystals  envelop  the  anodes  so  tightly  that 
the  current  cannot  reach  the  bath.  Besides,  too  concentrated 
baths  generally  produce  discolored  deposits,  as,  for  instance, 
too  concentrated  nickel  baths,  which  yield  a  dark  and  spotted 
deposit. 

Hence  in  summer,  when  the  bath  has  a  higher  temperature, 
it  may  be  made  more  concentrated  than  in  winter.  If  crystals 
are  separated  out,  even  when  the  bath  shows  a  temperature  of 
58°  F.,  it  must  be  diluted  with  water  until  the  formation  of  crys- 
tals ceases,  after  those  which  have  been  formed  have  been  dis- 
solved in  hot  water  added  to  the  bath. 

In  order  that  all  strata  of  the  bath  may  show  an  equal  con- 
tent of  metal,  it  is  advisable  in  the  evening,  after  the  day's  work 
is  done,  to  thoroughly  stir  up  the  solution  with  a  wooden  crutch. 
For  practical  reasons  the  baths  are  generally  made  one-quarter 
to  one-third  deeper  than  corresponds  to  the  lengths  of  the  ob- 
jects to  be  plated.  In  consequence  of  this,  the  strata  of  fluid 
between  the  anodes  and  the  objects  become  poorer  in  metal 
than  those  on  the  bottom,  and  the  object  of  stirring  up  is  to  re- 
store the  same  concentration  to  all  portions  of  the  bath. 

The  strata  of  fluid  which  come  in  contact  with  the  anodes  be- 


UNIVERSITY 


PROCESSES    OF   ELECTRO-DEPOSITION. 


163 


FIG.  104. 


come,  by  the  absorption  of  metal,  specifically  heavier  than  the 
other  strata,  and  sink  to  the  bottom ;  on  the  other  hand,  the 
strata  of  fluid  which  yield  metal  to  the  objects  become  specifi- 
cally lighter  and  rise  to  the  top.  A  partial  compensation  of 
course  takes  place  by  diffusion,  but  not  a  complete  one,  and 
from  this  cause  arise  several  evils.  The  heavier  and  more  satu- 
rated fluid  offering  greater  resistance  to  the  current,  the  anodes 
are  attacked  chiefly  on  the  upper  portions  where  the  specifically 
lighter  layer  of  fluid  is ;  practically  this  is  proved 
by  the  appearance  of  the  anodes  which,  at  first 
square,  after  being  for  some  time  used  assume  the 
shape  shown  in  Fig.  104. 

On  the  other  hand,  the  portions  of  the  cathodes 
(objects)  which  come  in  contact,  near  the  surface, 
with  strata  of  fluid  poorer  in  metal,  acquire  a  deposit 
of  less  thickness  than  the  lower  portions  which  dip 
into  the  bath  where  it  is  richer  in  metal.  Now,  if 
the  bath  also  contains  free  acid,  and  if  there  is  a  con- 
siderable difference  in  the  specific  gravity  of  the  lower  and 
upper  strata  of  fluid,  the  electrode,  which  touches  both  strata, 
produces  a  current,  the  effect  of  which  is  that  metal  dissolves 
from  the  upper  portions  and  deposits  upon  the  lower.  This 
explains  the  phenomenon  that  a  deposit  on  the  upper  portions 
of  the  objects  may  be  redissolved,  even  when  a  current,  which, 
however,  must  be  very  weak,  is  conducted  into  the  bath  from 
an  external  source. 

Many  authors,  therefore,  go  so  far  as  to  demand  that  during 
the  electro-plating  process  the  baths  should  be  kept  in  con- 
stant agitation  by  mechanical  means.  This,  however,  is 
scarcely  necessary,  because  a  homogeneity  of  the  solution  is 
to  a  certain  extent  effected  by  the  agitation  of  the  fluid  in 
suspending  and  taking  out  the  objects.  Hence  as  long  as 
objects  are  put  in  and  taken  out  an  agitation  naturally  takes 
place  in  which  all  the  strata  of  fluid  between  the  objects  and 
anodes  take  part,  while  only  the  deepest  strata,  which  do  not 
come  into  contact  with  the  objects  and  the  anodes,  remain  in 
a  state  of  stagnation. 


1 64  ELECTRO-DEPOSITION   OF   METALS. 

Constant  agitation  of  the  electro-plating  solution  is  of  ad- 
vantage only  in  silvering  and  in  the  galvano-plastic  reproduc- 
tion in  the  acid  copper  bath,  in  which  the  objects  have  to 
remain  four  to  five  and  eight  to  ten  hours.  Some  authors  de- 
mand constant  agitation  for  the  more  rapid  removal  of  the 
bubbles  of  hydrogen  which  form  on  the  objects ;  but  the  same 
end  is  attained  without  complicated  contrivances,  by  the 
operator  accustoming  himself  to  strike  the  object-rod  a  slight 
blow  with  the  finger  each  time  he  suspends  an  object. 

The  degree  of  temperature  required  for  the  electro-plating 
solutions  has  already  been  discussed  on  page  86,  where  also 
the  means  have  been  given  by  which  too  cool  solutions  may 
be  brought  to  the  proper  degree  of  temperature.  Baths  which 
are  to  be  used  cold  should  under  no  circumstances  show  a 
temperature  below  59°  F.,  it  being  best  to  maintain  them  at 
between  64.5°  and  and  68°  F. 

Boiling  is   required   in   the   preparation  of   many  baths,  if, 

FIG.  105.  FIG.  106. 


after  cooling,  they  are  to  yield  good  and  certain  results.  The 
kettles  and  boiling-pans  used  for  the  purpose  are  of  various 
shapes,  hemispherical  or  with  flat  bottom,  and  are  made  of 
different  materials  (Figs.  105  and  106),  those  of  enameled 
iron,  or,  for  small  baths,  of  porcelain  or  earthenware,  being 
best.  The  enamel  of  the  iron  kettles  must  be  of  a  composi- 
tion which  is  not  attacked  by  the  bath.  Notwithstanding  their 
enamel  these  vessels  become  gradually  impregnated  with  the 
solutions  they  have  held,  and  it  is  dangerous  to  employ  them 
for  different  kinds  of  baths.  Thus,  an  enameled  kettle  which 
has  been  used  for  silvering  will  not  be  suitable,  even  after  the 


PROCESSES    OF   ELECTRO-DEPOSITION.  1 65 

most  thorough  washing,  for  a  gold  bath,  as  the  gilding  will 
certainly  be  white  or  green,  according  to  the  quantity  of  silver 
retained  by  the  vessel.  The  use  of  metal  vessels  should  be 
avoided ;  copper  and  brass  baths  may,  however,  be  boiled  in 
strong  copper  kettles,  though  they  are  somewhat  attacked. 
A  copper  kettle,  after  being  freed  from  grease  and  scoured 
bright,  may  be  provided  with  a  thick  deposit  of  nickel,  by  fill- 
ing it  with  a  nickel  bath,  connecting  it  with  the  negative  pole 
of  a  strong  battery  or  dynamo  machine,  and  suspending  in  it 
a  number  of  nickel  anodes  connected  with  the  positive  pole. 
Such  nickeled  kettle  may  be  used  for  boiling  nickel  baths, 
but  enameled  kettles  or  large  dishes  of  nickel-sheet  deserve 
the  preference. 

If  the  boiling  of  large  quantities  of  fluid  is  not  convenient, 
the  same  end  may  be  attained  by  thoroughly  working  the  bath 
for  a  few  days  with  the  electric  current.  Suspend  to  the  anode- 
rods  as  many  anodes  as  possible,  secure  to  the  object-rods  a 
few  plates  of  the  same  metal,  and  introduce  a  current  of  medium 
strength,  until  an  object,  from  time  to  lime,  suspended  in  the 
bath  acquires  a  regular  deposit.  This  method  is  frequently 
and  very  successfully  used  for  large  brass  baths. 

Nickel  baths  as  a  rule  do  not  require  actual  boiling,  but  the 
nickel  and  certain  conducting  salts  which  together  form  the 
nickel  bath  dissolve  with  difficulty  in  cold  water,  and  for  this 
reason  solution  is  effected  in  hot  water. 

If  for  the  preparation  of  nickel  baths,  nickel  salts  dissolving 
with  difficulty  have  to  be  dissolved  with  the  assistance  of  heat 
and  a  suitable  kettle  is  wanting,  the  following  procedure  may 
be  adopted  :  Bring  water  in  a  clean,  bright  copper  kettle  to  the 
boiling  point,  pour  the  hot  water  into  a  clean  wooden  bucket 
having  a  capacity  of  8  to  10  quarts,  introduce  the  amount  of 
nickel  salt  corresponding  to  this  quantity  of  water,  and  stir  wiUi 
a  piece  of  wood  until  solution  is  complete. 

However,  with  large  baths  this  process  would  require  too 
much  time,  and  it  is,  therefore,  better  to  have  a  large  oval  or 
round  wooden  vat  lined  with  pure  sheet  lead  and  provided  with 


1 66  ELECTRO-DEPOSITION   OF   METALS. 

a  lead  coil  for  the  introduction  of  steam  by  means  of  which  the 
contents  of  the  vat  are  brought  to  the  boiling-point. 

If  the  prepared  and  boiled  solutions  are  not  entirely  clear, 
they  have  to  be  filtered,  which  for  large  baths  is  best  effected 
with  bags  of  fine  felt ;  and  for  smaller  baths,  especially  those  of 
the  noble  metals,  with  filtering  paper. 

To  secure  lasting  qualities  to  the  baths,  they  must  be  care- 
fully protected  from  every  possible  contamination.  When  not 
in  use  for  plating  they  should  be  covered  to  keep  out  dust. 
The  objects  before  being  placed  in  the  baths  should  be  free 
from  adhering  scouring  material  or  dipping  fluid,  which  other- 
wise might,  in  time,  spoil  the  bath.  The  cleansing  of  the  anode 
and  object  rods  by  means  of  sand-paper,  or  emery-paper, 
should  never  be  done  over  the  bath,  so  as  to  avoid  the  danger 
of  the  latter  being  contaminated  by  the  oxides  of  the  metal 
constituting  the  rods  falling  into  it.  When  a  visible  layer  of 
dust  has  collected  upon  the  bath,  it  must  be  removed,  as  other- 
wise particles  of  dust  might  deposit  upon  the  articles  and  pre- 
vent an  intimate  union  of  the  deposit  with  the  basis-metal. 
With  large  baths  the  removal  of  the  layer  of  dust  is  readily 
effected  by  drawing  a  large  piece  of  filtering  or  tissue  paper 
over  the  surface,  and  repeating  the  operation  with  fresh  sheets 
of  clean  paper  until  all  the  dust  is  removed.  Small  baths 
should  be  filtered. 

The  choice  of  anodes  is  also  an  important  factor  for  keeping 
the  baths  in  good  condition,  as  well  as  for  obtaining  good 
results.  The  anodes  should  always  consist  of  the  metal  which 
is  deposited  from  the  solution ;  and  the  metal  used  for  them 
must  be  pzire  and  free  from  all  admixtures.  To  replace  as 
much  as  possible  the  metal  withdrawn  from  the  bath  by  the 
electro-plating  process,  the  anodes  must  be  soluble ;  and  it  is 
wrong  if,  for  instance,  nickel  baths  are  charged  with  insoluble 
anodes  of  carbon ;  or  for  smaller  baths,  of  sheet  platinum. 
Such  insoluble  anodes  cause  a  steady  and  rapid  declination  in 
the  content  of  metal,  an  excessive  formation  of  acid  in  the  bath, 
and,  by  the  detachment  of  particles  of  carbon,  a  contamination 


PROCESSES    OF   ELECTRO-DEPOSITION.  167 

of  the  solution.  Further  particulars  in  regard  to  anodes  will  be 
given  in  discussing  the  separate  baths. 

When  upon  a  pure  metallic  surface  another  metal  is  electro- 
deposited,  the  first  portion  of  the  deposit  penetrates  into  the 
basis-metal,  thus  forming  an  alloy.  This  may  be  readily  proved 
by  repeating  Gore's  experiments  :  If  a  thick  layer  of  copper  be 
precipitated  upon  a  platinum  sheet,  and  then  heated  to  a  dark 
red  heat,  the  deposit  can  be  entirely  peeled  off;  by  then  heat- 
ing the  platinum  sheet  with  nitric  acid,  and  thoroughly  wash- 
ing with  water,  it  appears,  after  drying,  entirely  white  and  pure. 
By  re-heating  the  sheet,  the  surface  becomes  again  blackened 
by  cupric  oxide,  and  by  frequently  repeating  the  same  opera- 
tion a  fresh  film  of  cupric  oxide  will  always  be  obtained. 

This  penetration  of  the  deposit  into  the  basis-metal,  however, 
does  not  merely  take  place  during  electro-plating,  but  also  later 
on ;  and  it  may  frequently  be  observed  that,  for  instance,  zinc 
objects  only  slightly  coppered  or  brassed,  after  some  time  be- 
come again  white.  Since  this  also  happens  when  the  deposits 
are  protected  by  a  coat  of  lacquer  against  atmospheric  influ- 
ences, the  only  explanation  of  the  phenomenon  can  be  that  the 
deposit  is  absorbed  by  the  basis-metal,  which  is  also  confirmed 
by  analysis.  This  fact  must  be  taken  into  consideration  if  dur- 
able deposits  are  to  be  produced. 

To  guarantee  good  performance  an  electro-plating  bath  must 
fulfil  the  following  conditions:  — 

1.  It  must  possess  good  working  capacity. 

2.  It  must  exert  a  sufficiently  dissolving  action   upon  the 

anode. 

3.  It  must  reduce  the  metal  in  abundance  and  in  a  reguline 

state.  . 

4.  It  must  not  be  chemically  decomposed  by  the  metals  to 

be  plated,  hence  not  by  simple  immersion ;  the  adher- 
ence of  the  deposit  to  the  basis-metal  being  in  this  case 
impaired. 

5.  It  must  not  be  essentially  decomposed  by  air  and  light. 


1 68  ELECTRO-DEPOSITION   OF   MEl'ALS. 

Reduction  of  metals  without  a  battery  (electro-deposition  by 

contact) . 

We  may  here  appropriately  mention  the  reduction  of  metals 
which  takes  place  by  the  contact  of  two  metals  in  one  fluid  without 
the  aid  of  an  exterior  source  of  current.  That  an  electric  cur- 
rent is  thereby  generated  has  been  previously  explained :  one 
metal,  by  coming  in  contact  with  a  more  electro-positive  one, 
becomes  electro-negative  and  decomposes  the  fluid.  If  the 
latter  is  a  metallic  solution,  and  the  metal  contained  in  it  not 
more  strongly  electro-negative  than  the  negatively  excited  metal, 
a  separation  of  metal  takes  place  in  consequence  of  decomposi- 
tion. This  process  is  termed  electro- deposition  by  contact.  Gen- 
erally the  metals  which  are  to  be  coated  are  brought  in  contact 
with  a  bright  rod  of  zinc,  the  latter  being  a  highly  electro- 
positive metal.  The  zinc  is  allowed  to  dip  in  only  so  far  as  to 
secure  a  sure  contact  with  the  metal  to  be  coated. 

The  contact  of  one  metal  with  two  fluids  or  that  of  two 
metals  in  two  fluids,  presents  similar  phenomena,  an  electric 
current  with  visible  action  manifesting  itself,  and  in  the  latter 
case  we  have  a  complete  element.  By  dipping  the  more 
electro-negative  metal  in  a  metallic  solution  whose  metal  is  not 
more  electro-negative,  the  metal  separates  from  the  solution 
upon  the  metallic  strip  dipping  in.  While  by  the  contact  of 
one  metal  with  another  in  one  fluid,  only  thin  deposits  can  be 
produced,  and  by  coating  the  electro-negative  metal  with  the 
separated  metal,  the  contact-current  loses  some  of  its  original 
strength,  by  immersing  two  metals  in  two  fluids,  deposits  of 
considerable  thickness  can  under  certain  conditions  be  pro- 
duced, as,  for  instance,  with  the  galvano-plastic  cell  apparatus, 
which  will  be  discussed  later  on. 

A  reduction  of  metal  can  also  be  brought  about  by  dipping 
one  metal  into  one  fluid.  This  may  take  place  in  consequence 
of  the  simple  solution  of  the  metal  dipped  in,  and  hence  the 
separation  may  be  conceived  as  a  simple  chemical  action.  In 
how  far  electric  currents  manifest  themselves  and  co-operate 
thereby  is  still  undecided.  It  is  only  known  that  the  electro- 


DEPOSITION   OF  NICKEL   AND   COBALT.  169 

positive  metals,  such  as  zinc,  tin,  iron,  copper,  can  reduce  the 
electro- negative  metals,  such  as  mercury,  silver,  gold,  etc., 
from  the  solutions  of  their  salts,  and  that  the  reduction  is  the 
more  rapid  and  the  stronger  the  more  electro-positive  the 
metal  dipped  in  is,  and  the  more  electro-negative  the  dissolved 
metal  is. 

Upon  this  action  is  based  coppering,  silvering,  gilding,  etc., 
by  immersion. 


CHAPTER  VII. 

DEPOSITION  OF  NICKEL  AND  COBALT. 

i.  NICKELING. 

ALTHOUGH  nickel-plating  is  of  comparatively  recent  origin, 
it  shall  be  first  described,  since  chiefly  by  reason  of  the  devel- 
opment of  the  dynamo-electrical  machine  it  has  steadily  grown 
in  popularity  and  become  an  industry  of  great  magnitude  and 
importance.  The  great  popularity  which  nickel-plating  enjoys 
is  due  to  the  excellent  .properties  of  the  nickel  itself;  the 
almost  silvery  whiteness  of  the  metal,  its  cheapness  as  com- 
pared with  silver,  and  the  hardness  of  the  electro-deposited 
metal,  which  give  the  coating  great  power  to  resist  wear  and 
abrasion ;  its  capability  of  taking  a  high  polish ;  the  fact  that 
it  is  not  blackened  by  the  action  of  sulphurous  vapors  which 
rapidly  tarnish  silver,  and  finally  the  fact  that  it  exhibits  but 
little  tendency  to  oxidize  even  in  the  presence  of  moisture. 

Properties  of  nickel. — Pure  nickel  is  a  lustrous,  silvery  white 
metal  with  a  slight  steel-gray  tinge.  It  is  hard,  malleable  and 
ductile.  Its  specific  gravity  varies  from  8.3  (cast  nickel  plates) 
to  9.3  (wrought  or  rolled  plates).  It  melts  at  about  the  same 
temperature  as  iron,  but  is  more  fusible  when  combined  with 
carbon.  It  is  slightly  magnetic  at  ordinary  temperatures,  but 
loses  this  property  on  heating  to  680°  F. 


I/O  ELECTRO-DEPOSITION   OF   METALS. 

The  metal  is  soluble  in  dilute  nitric  acid,  concentrated  nitric 
acid  rendering  it  passive,  i.  e.,  insoluble.  In  hydrochloric  and 
sulphuric  acids  it  dissolves  very  slowly,  especially  when  in  a 
compact  state. 

Certain  articles,  for  instance  hot  fats,  strongly  attack  nickel, 
while  vinegar,  beer,  mustard,  tea,  and  other  infusions  produce 
stains ;  hence,  the  nickeling  of  culinary  utensils  or  the  use  of 
nickel-plated  sheet-iron  for  culinary  utensils  cannot  be  recom- 
mended. 

The  chemical  equivalent  of  nickel  is  29.5. 

Nickel  baths. — The  first  requisite  in  preparing  nickel  baths  is 
the  use  of  absolutely  pure  chemicals,  and  in  choosing  the  nickel 
salts  to  be  especially  careful  that  they  are  free  from  salts  of  iron, 
copper,  and  other  metals.  Furthermore,  it  is  not  indifferent 
what  kind  of  nickel  salt  is  used,  whether  nickel  chloride,  nickel 
sulphate,  the  double  sulphate  of  nickel  and  ammonium,  etc.,  but 
the  choice  of  the  salt  depends  chiefly  on  the  nature  of  the  metal 
which  is  to  be  nickeled.  There  are  a  large  number  of  general 
directions  for  nickel  baths,  of  which  nickel  chloride,  ammonio- 
nickel  chloride,  nickel  nitrate,  etc.,  form  the  active  constituents, 
and  yet  it  would  be  a  grave  mistake  to  use  these  salts  for  nickel- 
ing iron,  because  the  liberated  acid,  if  not  immediately  and 
completely  fixed  by  the  anodes  in  dissolving,  imparts  to  the  iron 
objects  a  great  tendency  to  the  formation  of  rust.  Iron  objects 
nickelled  in  such  a  bath,  to  be  sure,  come  out  faultless,  but  in  a 
short  time,  even  if  stored  in  a  dry  place,  portions  of  the  nickel 
layer  will  be  observed  to  peel  off,  and  by  closely  examining 
such  objects  it  will  be  seen  that  under  the  deposit  of  nickel  a 
layer  of  rust  has  formed  which  actually  tears  the  nickel  off. 
The  use  of  nickel  sulphates  or  of  the  salts  with  organic  acids  is, 
therefore,  considered  best.  It  might  be  objected  that  the 
liberated  sulphuric  acid  produces  in  like  manner  a  formation 
of  rust  upon  the  iron  objects ;  but  according  to  long  experience 
and  many  thorough  examinations  such  is  not  the  case,  the 
tendency  to  the  formation  of  rust  being  only  imparted  by  the 
use  of  the  chloride  and  nitrate.  The  use  of  nickel  salts  with 


DEPOSITION   OF  NICKEL   AND    COBALT.  I /I 

organic  acids  is  in  many  cases  more  advantageous  than  that  of 
the  sulphates,  but  such  salts  are  considerably  dearer,  and  hence 
they  are  less  frequently  employed;  in  many  prepared  nickeling 
salts  they  form  the  active  constituent.  The  composition  of  the 
conducting  salts  requires  the  same  deliberation  as  that  of  the 
nickeling  salts.  To  decrease  the  resistance  of  the  nickel  solu- 
tions, conducting  salts  are  added  to  them,  which  are  also 
partially  decomposed  by  the  current.  Like  the  use  of  nickel 
chloride  in  nickeling  iron,  an  addition  of  ammonium  chloride, 
which  is  much  liked,  cannot  be  recommended,  though  the  sub- 
sequent easy  reduction  of  nickel  invites  its  employment. 

For  copper  and  its  alloys,  zinc,  etc.,  the  chlorine  combina- 
tions may  be  used,  but  for  nickeling  iron  they  must  be  avoided 
as  the  source  of  future  evils.  The  use  of  sodium  sulphide, 
sodium  nitrate,  barium  oxalate,  ammonium  nitrate,  sodium  sul- 
phate, and  ammonia-alum  as  conducting  salts,  which  has 
been  recommended  by  various  authors,  is  unsuitable.  With 
few  exceptions,  which  will  be  given  later  on,  the  best  basis  for 
the  conducting  salt,  according  to  Bottger  and  Adams,  is  am- 
monia, especially  in  the  form  of  ammonium  sulphate  or  hydro- 
chlorate,  provided  the  latter  is  not  used  for  baths  for  nickeling 
iron. 

Some  other  additions  to  the  nickeling  bath  which  are  claimed 
to  effect  a  pure  silvery-white  reduction  of  the  nickel  have  been 
recommended  by  various  experts.  Thus,  the  presence  of  small 
quantities  of  an  organic  acid  has  been  proposed ;  for  instance, 
boric  acid  by  Weston,  benzoic  acid  by  Powell,  and  citric  acid 
or  acetic  acid  by  others.  The  presence  of  small  quantities  of  a 
free  acid  effects  without  doubt  the  reduction  of  a  whiter  nickel 
than  is  the  case  with  a  neutral  or  alkaline  solution.  Hence  a 
slightly  acid  reaction  of  the  nickeling  bath,  due  to  the  presence 
of  citric  acid,  etc.,  with  the  exclusion  of  the  strong  acids  of  the 
metalloids,  can  be  highly  recommended.  The  quantity  of  free 
acid  must,  however,  not  be  too  large,  as  this  would  cause  the 
deposit  to  peel  off. 

Boric  acidy  recommended  by  Weston  as  an  addition  to  nickel- 


ELECTRO- DEPOSITION   OF   METALS. 

ing  and  all  other  baths,  has  a  favorable  effect  upon  the  pure 
white  reduction  of  the  nickel,  especially  in  nickeling  rough 
castings,  i.  e.,  surfaces  not  ground.  Weston  claims  that  boric 
acid  prevents  the  formation  of  basic  nickel  combinations  on  the 
objects,  and  that  it  makes  the  deposit  of  nickel  more  adherent, 
softer,  and  more  flexible.  Whether  with  a  correct  current- 
strength,  basic  nickel  salts,  to  which  the  yellowish  tone  of  the 
nickeling  is  said  to  be  due,  are  separated  on  the  cathode,  is  not 
yet  proved,  and  would  seem  more  than  doubtful.  The  action 
of  the  boric  acid  has  not  yet  been  scientifically  explained,  but 
numerous  experiments  have  shown  that  the  deposition  of  nickel 
from  nickel  solution  containing  boric  acid  is  neither  more  ad- 
herent nor  softer  and  more  flexible  than  that  from  a  solution 
containing  small  quantities  of  a  free  organic  acid.  Just  the 
contrary,  the  deposition  is  harder  and  more  brittle  in  the  pres- 
ence of  boric  acid,  and  different  results  may  very  likely  be  due 
to  the  employment  of  currents  of  varying  strength.  A  weak 
current  always  and  under  all  conditions  causes  the  deposition 
of  a  harder  and  more  brittle  nickel  than  a  current  of  medium 
strength;  and  in  order  to  judge  the  quality  of  the  deposited 
nickel  from  baths  of  varying  composition,  the  surface  of  the 
objects  and  of  the  anodes  must  always  be  the  same,  and  cur- 
rents of  equal  quantity  and  electro-motive  force  be  conducted 
into  the  bath.  Weston's  bath  will  be  spoken  of  later  on. 
Powell's  proposition  for  the  use  of  benzoic  acid  need  scarcely 
be  taken  seriously,  since  the  results  from  baths  containing  it 
differ  in.  no  respect  from  those  without  it. 

Before  giving  suitable  formulae  for  the  composition  of  nickel 
baths,  it  will  be  necessary  to  discuss  the  means  of  determining 
their  acidity  and  alkalinity.  As  previously  mentioned,  a  nickel 
bath,  to  yield  a  beautiful  white  deposit,  should  contain  only  a 
small  quantity  of  free  acid ;  too  much  acid  preventing  the  firm 
adherence  of  the  deposit,  while  alkaline  and  even  neutral  baths 
do  not  yield  nickel  of  a  pure  white  color,  but  of  a  somewhat 
darker  tone.  A  bath  is  neutral  when  it  contains  neither  free 
acid  nor  free  alkali,  which  is  recognized  by  neither  blue  nor  red 


DEPOSITION   OF  NICKEL   AND    COBALT.  1/3 

litmus-paper*  being  changed  by  the  solution.  Blue  litmus- 
paper  is  colored  red  by  acid  fluids,  and  red  litmus-paper  blue 
by  alkaline  fluids.  By  simultaneously  dipping  one-half  of  a 
strip  of  blue  and  of  red  litmus-paper  in  the  solution,  the  re- 
action of  the  fluid  can  be  judged  from  the  change  in  color  and 
the  rapidity  and  intensity  of  its  appearance.  If  a  bath  which, 
like  most  nickel  baths,  is  to  work  with  only  a  slight  reaction, 
immediately  and  intensely  reddens  blue  litmus-paper,  a  suitable 
alkali  has  to  be  added  until  the  coloration  of  a  fresh  strip  of 
litmus-paper  appears  slower  and  less  intense.  If,  on  the  other 
hand,  the  test  shows  that  red  litmus-paper  becomes  blue,  and 
that  consequently  the  bath  is  alkaline,  a  slight  acid  reaction  is 
restored  by  the  gradual  addition  of  citric  acid  or  another  acid 
suitable  to  the  composition  of  the  bath.  Baths  made  with 
boric  acid  form  an  exception,  and  must  work  with  a  strong 
acid  reaction. 

I.  The  most  simple  nickel  bath  consists  of  a  solution  of  8  to 
10  parts  by  weight  of  pure  nickel  ammonium  sulphate  in  100 
parts  by  weight  of  distilled  water.  If  too  acid,  the  solution  is 
neutralized  with  spirits  of  sal  ammoniac  to  a  slightly  acid  re- 
action. The  solution  is  prepared  by  boiling  the  salt  with  the 
corresponding  quantity  of  water,  using  in  summer  10  parts  of 
nickel  salt  to  100  of  water,  but  in  winter  only  8  parts,  to  pre- 
vent the  nickel  salt  from  crystallizing  out.  This  bath,  which 
is  frequently  used,  possesses,  however,  a  considerable  degree 
of  resistance  to  conduction,  and  hence  requires  a  strong  cur- 
rent for  the  deposition  of  the  nickel.  It  also  requires  cast 
nickel  anodes,  since  with  the  use  of  rolled  anodes  nickeling 
proceeds  in  a  very  sluggish  manner.  However,  the  cast  anodes 
rapidly  render  the  bath  alkaline,  necessitating  a  frequent  cor- 
rection of  the  reaction.  To  decrease  the  resistance,  recourse 
has  been  had  to  certain  conducting  salts,  and,  below,  the  more 
common  nickel  baths  will  be  discussed,  together  with  their 
mode  of  preparation  and  action,  as  well  as  their  availability  for 
certain  purposes. 

*  Blue  and  red  litmus-paper  must  be  kept,  each  by  itself,  in  well-closed  glass  jars. 


174  ELECTRO-DEPOSITION    OF   METALS. 

II.  Nickel  ammonium  sulphate  17  ozs.,  ammonium  sulphate 
17  ozs.,  distilled  water  10  quarts. 

Boil  the  salts  with  the  water,  and,  if  the  solution  is  too  acid, 
restore  its  neutrality  by  spirits  of  sal  ammoniac ;  then  grad- 
ually add  solution  of  citric  acid  until  blue  litmus-paper  is 
slowly  but  visibly  reddened.  The  bath  deposits  rapidly,  it 
possessing  but  little  resistance;  an  electro-motive  force  of  1.8 
to  2  volts  suffices,  and  all  metals  (zinc,  lead,  tin,  and  Britannia, 
after  previous  coppering)  can  be  nickeled  in  this  bath.  How- 
ever, upon  rough  castings  and  iron  a  pure  white  deposit  is 
difficult  to  obtain,  frequent  scratch-brushing  with  a  medium 
hard  steel  brush  being  required.  On  account  of  the  great 
content  of  sulphate  of  ammonium  in  the  bath,  the  nickel  de- 
posit piles  up  especially  on  the  lower  portions  of  the  objects, 
which,  in  consequence,  readily  become  dull  (burn  or  over- 
nickel,  for  which  see  later  on),  while  the  upper  portions  are 
not  sufficiently  nickeled.  For  this  reason  the  objects  must  be 
frequently  turned  in  the  bath  so  that  the  lower  portions  come 
uppermost.  This  piling  up  of  the  deposit  also  frequently  pre- 
vents the  latter  from  acquiring  a  uniform  thickness. 

III.  Nickel  ammonium  sulphate  25}^  ozs.,  ammonium  sul- 
phate 8  ozs.,  crystallized  citric  acid   i$£  ozs.,  water  10  to   12 
quarts. 

This  bath  is  prepared  in  the  same  manner  as  the  preceding, 
the  salts  being  dissolved  in  boiling  water,  and  ammonia  added 
until  blue  litmus-paper  is  only  slightly  reddened. 

This  bath  requires  a  somewhat  greater  electro-motive  force 
than  the  preceding,  or  about  2  to  2.2  volts.  The  formation 
of  the  nickel  deposit  is,  however,  more  uniform,  of  a  beautiful 
white  color,  dense  and  hard,  and  consequently  bears  polishing 
without  danger  of  the  nickel  grinding  off,  even  if  not  very 
thickly  plated.  It  is  very  suitable  for  nickeling  ground  surgi- 
cal instruments,  as  well  as  all  ground  iron  articles  which  are  to 
be  thickly  and  solidly  plated,  and  for  heavy,  solid  nickeling  of 
copper,  brass,  bronze,  etc.  It  is  much  used  in  this  country, 
either  with  or  without  the  addition  of  citric  acid. 


DEPOSITION    OF  NICKEL   AND    COBALT.  175 

If,  after  working  for  some  time,  the  bath  loses  conducting 
power,  the  objects,  with  the  use  of  the  proper  current,  become 
blackish  without  a  reduction  of  nickel  being  perceptible;  while 
with  a  stronger  current  the  objects  are  nickeled  white,  but  the 
deposit  readily  peels  off.  In  this  case  the  conducting  power 
has  to  be  increased  by  the  addition  of  ammonium  sulphate. 
The  bath  should  always  be  kept  so  that  it  shows  a  slightly 
acid  reaction.  It  is  best  to  use  rolled  anodes. 

IV.  Nickel  ammonium  sulphate  23  ozs.,  ammonium  chloride 
(crystallized)  11^2  ozs.,  water  10  to  12  quarts. 

The  bath  is  prepared  in  the  same  manner  as  given  for  II. 
and  III.  It  nickels  very  rapidly  and  quite  white,  but  the  de- 
posit is  soft,  and  hence  care  must  be  had  in  polishing  upon 
cloth  or  felt  bobs,  the  corners  and  edges  of  the  objects  espec- 
ially requiring  careful  handling.  On  account  of  the  danger  of 
peeling  off,  a  heavy  deposit  of  nickel  cannot  be  obtained  in  this 
bath,  since,  in  consequence  of  the  rapid  precipitation,  the  de- 
posit condenses  and  absorbs  hydrogen,  is  formed  with  a  coarser 
structure,  and  turns  out  less  uniform  and  dense.  These  phe- 
nomena are  a  hindrance  to  a  heavy  deposit,  which,  if  it  is  to 
adhere,  must  be  homogeneous  and  dense.  As  previously  men- 
tioned, baths  with  the  addition  of  chlorides  as  well  as  those  pre- 
pared with  nickel  chloride  and  nickel  nitrate  are  not  suitable  for 
the  solid  nickeling  of  iron  ;  they  are,  however,  well  adapted  to 
the  rapid  light  nickeling  of  cheap  brass  articles.  The  electro- 
motive force  required  for  this  bath  is  1.8  volts. 

V.  Nickel  chloride  (crystallized)  17^  ozs.,  ammonium  chlor- 
ide (crystallized)  17^  ozs.,  water  12  to  15  quarts. 

The  bath  is  prepared  in  the  same  manner  as  given  for  II.  and 
III.,  though  solution  may  be  effected  cold.  The  bath  precipi- 
tates very  readily,  and  is  especially  liked  for  nickeling  zinc  cast- 
ings. Tension  of  current,  1.5  to  1.75  volts. 

For  nickeling  iron  this  bath  has  the  same  disadvantages,  and 
even  to  a  still  greater  extent  than  the  preceding. 

VI.  Baths  containing  boric  acid. — Weston  recommends  the 
following  composition  for  nickel  baths:   Nickel  chloride 


1/6  ELECTRO-DEPOSITION   OF   METALS. 

ozs.,  boric  acid  7  ozs.,  water  20  quarts ;  or,  nickel-ammonium 
sulphate  35  ozs.,  boric  acid  17  j£  ozs.,  water  25  to  30  quarts. 
Both  solutions  are  said  to  be  improved  by  adding  caustic 
potash  or  caustic  soda  so  long  as  the  precipitate  formed  by  the 
addition  dissolves.* 

These  compositions,  however,  cannot  be  recommended, 
chiefly  because  the  baths  work  faultlessly  for  a  comparatively 
short  time  only;  all  kinds  of  disturbing  phenomena  make  their 
appearance,  the  deposit  being  no  longer  white  but  blackish,  and 
the  baths  soon  failing  entirely.  Kaselowsky's  formula  yields 
similar  results.  It  is  prepared  by  dissolving,  with  the  assistance 
of  heat,  35%!  ozs.  of  nickel-ammonium  sulphate  and  i/3/^  ozs.  of 
boric  acid  in  20  quarts  of  water.  If  an  entirely  neutral  double 
sulphate  has  not  been  employed,  this  bath  also  generally  fails 
after  two  or  three  months'  use.  The  cause  of  this  has  to  be 
primarily  sought  in  the  fact  that  baths  prepared  with  boric  acid 
require  according  to  their  composition  a  definite  proportion 
between  the  rolled  and  cast  nickel  anodes  present  in  the  bath. 
If  rolled  anodes  are  exclusively  used,  free  sulphuric  acid  is  soon 
formed,  which  causes  energetic  evolution  of  hydrogen  on  the 
articles,  but  prevents  a  vigorous  deposit  and  imparts  to  the 
latter  a  tendency  to  peel  off.  The  same  thing  happens  when 
a  nickel  salt  not  entirely  neutral  has  been  used  in  the  prepara- 
tion of  the  bath.  If,  on  the  other  hand,  cast  nickel  anodes 
alone  are  employed,  the  bath  soon  becomes  alkaline,  with 
turbidity  and  the  formation  of  slime,  and  the  deposit  turns  out 
gray  and  dull  before  it  possesses  sufficient  thickness. 

From  the  foregoing  it  will  be  readily  understood  that  the 
nickel  salt  used  must  be  neutral  and  that  the  proportion  of 
rolled  to  cast  anodes  must  be  so  chosen  that  the  free  sul- 
phuric acid  formed  on  the  cast  anodes  is  neutralized,  but  that 
the  acidity  of  the  bath  dependent  on  the  free  boric  acid  is  con- 
stantly maintained. 

Such  a  bath  containing  boric  acid  may  advantageously  be 
prepared  as  follows: 

*  Dingler's  Journal,  235,  p.  404.     Wagner's  Jahresbericht,  1883,  p.  146. 


DEPOSITION   OF   NICKEL   AND    COBALT. 

VII.  Nickel-ammonium  sulphate  21  ozs.,  chemically  pure 
nickel  carbonate  I  ^  ozs.,  chemically  pure  boric  acid  (crys- 
tallized) 10^  ozs.,  water  10  to  12  quarts. 

Boil  the  nickel-ammonium  sulphate  and  the  nickel  carbonate 
in  the  water  until  the  evolution  of  bubbles  of  carbonic  acid 
ceases  and  blue  litmus  paper  is  no  longer  reddened.  After 
allowing  sufficient  time  for  settling,  decant  the  solution  from 
any  undissolved  nickel  carbonate  and  add  the  boric  acid. 
Boil  the  whole  a  few  minutes  longer,  and  allow  to  cool.  If  the 
nickel  salt  contains  no  free  acid,  boiling  with  the  nickel  car- 
bonate may  be  omitted.  The  solution  shows  a  strongly  acid 
reaction  which  must  not  be  removed  by  alkaline  additions. 

The  proportion  of  cast  to  rolled  anodes  used  in  this  bath  is 
dependent  on  the  quality  of  the  anodes.  The  use  of  readily 
soluble  cast  anodes  requires  the  suspension  in  the  bath  of 
more  rolled  anodes  than  when  cast  anodes  dissolving  with 
difficulty  are  employed,  since  the  latter  in  consequence  of 
rapid  cooling  have  a  surface  not  readily  attacked.  The  pro- 
portion has  likewise  to  be  changed,  with  the  use  of  soft  or 
hard-rolled  anodes.  Hence  the  proper  proportion  will  have 
to  be  established  by  frequently  testing  the  reaction  of  the 
bath.  For  testing  the  bath  the  following  rules  may  be  laid 
down:  Blue  litmus-paper  must  always  be  perceptibly  and  in- 
tensely reddened,  but  congo-paper  should  not  change  its  red 
color,  for  if  the  latter  turns  blue  it  is  an  indication  of  the  pres- 
ence of  free  sulphuric  acid  in  the  bath,  which  has  to  be 
neutralized  by  the  careful  addition  of  solution  of  soda  or 
potash  until  a  fresh  piece  of  congo-paper  dipped  in  the  bath 
remains  red.  Ammonia  cannot  be  recommended  for  neutral- 
izing free  sulphuric  acid  in  this  bath.  Red  litmus-paper  must 
remain  red,  for  if  it  turns  blue,  the  bath  has  become  alkaline 
and  fresh  boric  acid  has  to  be  dissolved  in  the  previously 
heated  bath  until  a  fresh  piece  of  blue  litmus-paper  acquires 
an  intense  red  color. 

The  bath  prepared  according  to  the  above  formula  (VII) 
requires  an  electro-motive  force  of  about  2.3  to  2.5  volts. 

12 


178  ELECTRO-DEPOSITION   OF   METALS. 

Below  are  given  a  few  other  formulae  for  nickel  baths  which 
may  be  advantageously  used  for  special  purposes,  but  not  for 
equally  good  nickeling  of  all  kinds  of  metals. 

VIII.  Nickel   sulphate    lo^J   ozs.,  potassium   citrate   7  ozs., 
ammonium  chloride  7  ozs.,  water  10  to  12  quarts. 

To  prepare  the  bath  dissolve  10^  ounces  of  nickel  sulphate 
and  ^y2  ounces  of  pure  crystallized  citric  acid  in  water; 
neutralize  accurately  with  caustic  potash,  and  then  add  the 
ammonium  chloride.  This  bath  is  especially  adapted  for  the 
rapid  nickeling  of  polished,  slightly  coppered  zinc  articles.  The 
deposition  is  effected  with  a  very  feeble  current,  without  the 
formation  of  black  streaks,  such  as  are  otherwise  apt  to  appear 
in  nickeling  with  a  weak  current.  The  deposit  itself  is  dull 
and  somewhat  gray,  but  acquires  a  very  fine  polish  and  pure 
white  color  by  slight  manipulation  upon  the  polishing  wheels. 
With  a  stronger  current  the  bath  is  also  suitable  for  the  direct 
nickeling  of  zinc  articles;  it  must,  however,  be  kept  strictly 
neutral.  The  bath  works  with  rolled  anodes,  and  but  seldom 
requires  a  correction  of  the  reaction. 

IX.  Nickel  phosphate  8^  ozs.,  sodium  pyrophosphate  26^ 
ozs.,  water   10  to  15  quarts.     Dissolve  the  sodium  pyrophos- 
phate in  water,  heat  the  solution  to  about  167°  F.  and  add  the 
nickel  phosphate  with  constant  stirring.     Nickel  phosphate  is 
obtained  as  a  pale  green  powder  by  precipitating  solution  of 
nickel  sulphate  with  sodium  phosphate. 

This  bath  yields  a  very  fine  dark  nickeling  upon  iron,  brass, 
and  copper,  as  well  as  directly \  without  previous  coppering,  upon 
sheet  zinc  and  zinc  castings,  and  may  be  advantageously  used 
for  decorative  purposes  where  darker  tones  of  nickel  are  de- 
manded. 

X.  A  fairly  good  nickel-bath  for  electro-platers  having  but  a 
feeble  current  at  their  disposal  is  obtained  from  a  solution  of 
nickel-ammonium    sulphate    22  J^    ozs.,   magnesium    sulphate 
iij^  ozs.,  water  10  to  12  quarts. 

This  bath  precipitates  readily  and  strongly,  and  a  heavy 
coating  can  also  be  deposited  upon  iron  without  fear  of  the 


DEPOSITION   OF   NICKEL   AND    COBALT.  179 

disagreeable  consequences  of  bath  IV. ;  even  zinc  may  be 
directly  nickeled  in  it  with  a  comparatively  feeble  current. 
The  deposit,  however,  turns  out  rather  soft,  with  a  yellowish 
tinge,  and  the  bath  does  not  remain  constant,  but  fails  after 
working  at  the  utmost  three  or  four  months,  the  anodes  being 
scarcely  attacked. 

Below  are  given  the  compositions  of  a  few  nickel  baths  which 
have  been  highly  recommended: — 

XL  Pure  nickel  sulphate  35  J^  ozs.,  neutral  ammonium  tar- 
trate  26^  ozs.,  tannin  77  grains,  water  20  quarts.  Neutral 
ammonium  tartrate  is  obtained  by  saturating  a  solution  of  tar- 
taric  acid  with  ammonia.  The  nickel  salt  must  also  be  neutral. 
For  this  purpose  dissolve  the  above-mentioned  ingredients  in  3 
or  4  quarts  of  water  and  boil  the  solution  for  l/£  hour,  then  add 
enough  water  to  make  20  quarts  of  fluid,  and  filter.  The  bath 
is  said  to  yield  a  very  white,  soft,  and  homogeneous  deposit  of 
any  desired  thickness,  without  roughness  or  danger  of  peeling 
off.  On  rough  or  polished  castings  thick  deposits  may  be  ob- 
tained at  a  cost  scarcely  exceeding  that  of  coppering.  Galvano- 
plastic  reproduction  may  also  be  effected  in  this  bath.  For 
those  who  wish  to  try  the  bath  it  may  be  mentioned  that  the 
most  suitable  current-strength  is  3.5  volts. 

XII.  An  English  formula  is  as  follows:   Dissolve  17^  ozs. 
of  nickel  sulphate,  9^   ozs.  of  tartaric  acid,  and  2j£  ozs.  of 
caustic  potash  in  10  quarts  of  water. 

The  addition  of  bisulphide  of  carbon  to  nickel  baths,  which 
has  been  recommended  by  Bruce,  is  not  advisable.  Ac- 
cording to  Bruce,  such  an  addition  prevents  the  nickel  de- 
posits from  becoming  dull  when  reaching  a  certain  thickness, 
but  repeated  experiments  made  strictly  in  accordance  with  the 
directions  given  did  not  confirm  this  statement. 

XIII.  For    nickeling    small    articles    the    following    bath    is 
claimed  to  yield  excellent  results :   Nickel-ammonium  sulphate 
64  ozs.,  ammonium  sulphate  20^  ozs.,  crystallized  citric  acid 

ozs. 
For  the  production  of  very  thick  deposits,  the  following  has 


180  ELECTRO-DEPOSITION   OF   METALS. 

been  recommended:  Nickel  ammonium  sulphate  16  ozs., 
sodium  citrate  10  ozs.,  water  10  quartos.  This  bath  is  said 
to  be  especially  useful  in  preparing  nickel  cliches.  However, 
numerous  experiences  proved  it  to  possess  the  disadvantages 
of  all  nickel  baths  prepared  with  large  quantities  of  organic 
combinations,  and  for  the  special  purpose  for  which  it  is  re- 
commended no  better  results  were  obtained  than  with  any 
other  nickel  bath  rationally  composed  for  heavy  deposits. 

In  some  works  on  galvanoplasty  a  solution  of  nickel  cyanide 
in  potassium  cyanide  is  recommended  for  nickeling,  but  ex- 
periments failed  to  obtain  a  proper  reduction  of  nickel. 

We  would  here  add  the  general  remark  that  fres/tfy  prepared 
nickel  baths  mostly  work  correctly  from  the  beginning,  though 
it  may  sometimes  happen  that  the  articles  first  nickeled  come 
from  the  bath  with  a  somewhat  darker  tone.  In  such  case  it  is 
advisable  to  suspend  a  few  anodes  to  the  cathode  and  allow  the 
bath  to  work  one  or  two  hours,  when  the  nickeling  will  proceed 
faultlessly. 

A  few  words  may  here  be  said  in  regard  to  what  may  be 
termed  a  nickel  bath  without  nickel  salt.  It  simply  consists  of  a 
15  to  20  per  cent,  solution  of  ammonium  chloride,  which  trans- 
fers the  nickel  from  the  anodes  to  the  articles.  Cast  anodes  are 
almost  exclusively  used  for  the  purpose,  and  deposition  may  be 
effected  with  quite  a  feeble  current.  Before  the  solution  ac- 
quires the  capacity  of  depositing,  quite  a  strong  current  has  to 
be  conducted  through  the  bath  until  the  commencement  of  a 
proper  reduction  of  nickel.  This  bath  is  only  suitable  for 
coloring  very  cheap  articles,  it  not  being  possible  to  produce 
solid  nickeling  with  it ;  and  it  is  here  mentioned  because  it  may 
serve  as  a  representative  of  a  series  of  other  electro-plating 
baths  in  which  the  transfer  of  the  metal  is  effected  by  sal 
ammoniac  solution  without  the  use  of  metallic  salts,  for  in- 
stance, iron,  zinc,  cobalt,  etc. 

Nickel  anodes. — Either  cast  or  rolled  nickel  plates  are  used  as 
anodes,  which  must  of  course  be  as  pure  as  it  is  possible  to  ob- 
tain them.  Every  impurity  of  the  anodes  passes  into  the  bath 


DEPOSITION   OF  NICKEL  AND    COBALT.  l8l 

and  jeopardizes  its  successful  working.  If  too  thin  the  anodes 
increase  the  resistance ;  for  small  baths  rolled  anodes  0.079 
inch  thick  are  generally  used,  and  as  a  rule  they  should  not  be 
less  than  0.039  mcn  thick.  For  larger  baths  it  is  better  to  use 
plates  from  o.n  to  0.19  inch  thick,  while  the  thickness  of  cast 
anodes  may  vary  between  o.n  and  0.39  inch,  according  to  the 
size  of  the  bath  and  the  purpose  for  which  it  is  to  be  used. 
The  use  of  insoluble  anodes  of  gas-carbon  or  platinum,  either 
by  themselves  or  in  conjunction  with  nickel  anodes,  as  fre- 
quently recommended,  is  not  advisable.  The  harder  and  the 
less  porous  the  nickel  anode  is,  the  less  it  is  attacked  in  the 
bath  and  the  less  it  fulfils  the  object  of  keeping  constant  the 
metallic  content  of  the  solution.  On  the  other  hand,  the  softer 
and  the  more  porous  the  anode  is,  the  more  readily  it  dissolves, 
because  it  conducts  the  current  better  and  presents  more  points 
of  attack  to  the  bath ;  and  the  more  it  is  dissolved,  the  more 
metal  is  conveyed  to  the  bath.  With  the  sole  use  of  rolled 
anodes  and  working  with  a  feeble  current,  free  acid  is  formed 
in  the  bath ;  on  the  other  hand,  by  working  with  cast  anodes 
alone,  the  bath  readily  becomes  alkaline.  Now  it  seems  that 
the  possibility  of  a  bath  also  becoming  alkaline  even  with  the 
sole  use  of  rolled  anodes,  especially  when  working  with  a  strong 
current,  has  led  to  the  proposal  of  suspending  in  the  bath,  be- 
sides the  nickel  anodes,  a  sufficient  number  of  insoluble  anodes 
in  order  to  effect  a  constant  neutrality  of  the  bath.  It  would 
lead  too  far  to  go  into  the  theory  of  the  secondary  decomposi- 
tions which  take  place  in  a  nickel  bath,  to  prove  that,  though 
neutrality  is  obtained,  it  can  only  be  done  at  the  expense  of 
the  metallic  content  of  the  bath.  Hence,  this  impracticable 
proposal  shall  here  be  overthrown  by  practical  reasons,  it  only 
requiring  to  be  demonstrated  that  in  baths  becoming  alkaline 
the  content  of  nickel  also  decreases  steadily  though  slowly. 
This  fact  in  itself  shows  that  in  order  to  save  the  occasional 
slight  labor  of  neutralizing  the  bath,  the  decrease  of  the  me- 
tallic content  should  not  be  accelerated  by  the  use  of  insoluble 
anodes.  For  larger  baths  the  use  of  expensive  platinum 


1 82  ELECTRO-DEPOSITION    OF   METALS. 

anodes  as  insoluble  anodes  need  not  be  taken  into  considera- 
tion, because  for  large  surfaces  of  objects  correspondingly  large 
surfaces  of  platinum  anodes  would  have  to  be  present,  as  other- 
wise the  resistance  of  thin  platinum  sheets  would  be  consider- 
able. But  such  an  expensive  arrangement  would  be  justifiable 
only  if  actual  advantages  were  obtained,  which  is  not  the  case, 
because,  though  the  platinum  does  absolutely  not  dissolve,  the 
deficiency  of  metallic  nickel  in  the  bath  caused  by  such  anodes 
must  in  some  manner  be  replaced.  The  insoluble  anodes  of 
gas-carbon  which  have  frequently  been  proposed  are  attacked 
by  the  bath  ;  particles  of  carbon  becoming  constantly  detached, 
and  floating  upon  the  bath,  deposit  themselves  upon  the  ob- 
jects and  cause  the  layer  of  nickel  to  peel  off.  Furthermore, 
by  the  use  of  nickel  anodes  in  conjunction  with  carbon  anodes, 
the  current,  on  account  of  the  greater  resistance  of  the  latter, 
is  forced  to  preferably  take  its  course  through  the  metallic 
anodes,  in  consequence  of  which  the  articles  opposite  the 
nickel  anodes  are  more  thickly  nickeled  than  those  under  the 
influence  of  the  carbon  anodes.  With  larger  objects  this  in- 
equality in  the  thickness  of  the  deposit  is  again  a  hindrance  to 
obtaining  layers  of  good  and  uniform  thickness,  such  as  are 
required  for  solid  nickeling.  Since  the  current  preferably 
seeks  its  compensation  through  these  separate  metallic  anodes, 
they  are  more  vigorously  attacked  than  when  nickel  plates 
only  are  suspended  in  the  bath. 

With  nickel  baths  which  contain  a  considerable  amount  of 
ammonium  chloride,  the  use  of  a  few  carbon  anodes  along  with 
the  rolled  nickel  anodes  may  be  permissible,  since  these  baths 
strongly  attack  even  the  rolled  anodes,  and  thereby  convey  to 
the  bath  sufficient  quantities  of  fresh  nickel.  Such  baths  con- 
taining ammonium  chloride,  as  a  rule,  become  very  rapidly 
alkaline,  so  that  frequent  neutralization  becomes  inconvenient. 
However,  in  this  case,  it  is  advisable  to  place  the  carbon  anodes 
in  small  linen  bags  which  retain  any  particles  of  carbon  becom- 
ing detached,  the  latter  being  thus  prevented  from  depositing 
upon  the  articles  in  the  bath. 


DEPOSITION   OF   NICKEL   AND    COBALT.  183 

According  to  long  practical  experience,  the  best  plan  is  to 
use  rolled  and  cast  anodes  together  in  one  bath.  The  propor- 
tion of  cast  to  rolled  anodes  depends  on  the  composition  of  the 
bath,  but  it  may  be  laid  down  as  a  rule,  that  baths  with  greater 
resistance  require  more  cast  anodes,  and  baths  with  less  re- 
sistance more  rolled  anodes.  Cast  anodes,  to  be  sure,  have  the 
disadvantage  of  soon  becoming  spongy,  and  crumbling  before 
being  entirely  used  up.  Furthermore,  the  surfaces  of  nickel 
anodes  cast  in  iron  moulds  are  so  hard  as  to  temporarily  resist 
the  action  of  the  bath,  while  the  interior  dissolves  only  partially, 
since,  on  the  one  hand,  the  oxygen  separating  on  the  anode, 
which  is  necessary  for  solution,  escapes  partially  unused,  and 
on  the  other,  the  intact  outer  layer  prevents  the  bath  from 
coming  in  contact  with  the  interior  of  the  anode. 

The  cast  anodes  suspended  to  the  ends  of  the  conducting  rods 
are  especially  strongly  attacked,  and,  therefore,  when  rolled 
and  cast  anodes  are  used  together,  it  is  best  to  suspend  the 
latter  more  towards  the  centre,  and  the  first  on  the  ends  of  the 
rods. 

These  disadvantages,  however,  are  not  sufficient  to  prevent 
the  use  of  a  combination  of  cast  and  rolled  anodes  when  re- 
quired by  the  composition  of  the  bath.  The  spongy  remnants 
are  thoroughly  washed  in  hot  water,  dried  and  sold. 

The  rolled  nickel  anodes  are  less  liable  to  corrosion,  and  may 
be  used  up  to  the  thickness  of  a  sheet  of  paper  before  they  fall 
to  pieces.  It  is,  however,  best  to  replace  them  by  fresh  anodes 
before  they  become  too  thin,  since  with  the  decrease  in  thick- 
ness their  resistance  increases. 

The  surface  of  the  anodes  suspended  in  the  baths  should  be 
at  least  as  large  as  that  of  the  articles  to  be  nickeled  ;  it  is,  how- 
ever, preferable  that  they  should  present  twice  or  three  times 
the  surface,  in  order  that  the  bath  may  be  kept  thoroughly 
saturated  with  nickel. 

It  is  best  to  allow  the  anodes  to  remain  quietly  in  the  bath, 
even  when  the  latter  is  not  in  use,  they  being  in  this  case  not 
attacked.  By  frequently  removing  and  replacing  them  they 


1 84  ELECTRO-DEPOSITION    OF   METALS. 

are  subject  to  concussion,  in  consequence  of  which  they 
crumble  much  more  quickly  than  when  remaining  quietly  in 
the  bath. 

In  the  morning,  before  nickeling  is  commenced,  the  anodes 
will  frequently  show  a  reddish  tinge,  which  is  generally  ascribed 
to  a  content  of  copper  in  the  bath  or  in  the  anodes.  This  red- 
dish coloration  also  appears  when  an  analysis  shows  the  anodes 
as  well  as  the  bath  to  be  absolutely  free  from  copper.  It  is 
very  likely  due  to  a  small  content  of  cobalt,  from  which  nickel 
anodes  can  never  be  entirely  freed.  It  would  seem  that  by  the 
action  of  a  feeble  current  cobaltous  hydrate  is  formed,  which 
however  immediately  disappears  on  conducting  a  strong  current 
through  the  bath. 

The  anodes  are  supported  by  nickel  wire  o.  II  to  0.19  inch 
thick,  or  by  strips  of  nickel  sheet  riveted  on. 

If  after  working  for  some  time  a  nickel  bath  has  become 
alkaline,  which  can  be  readily  determined  by  testing  with  litmus- 
paper,  its  neutrality  or  a  slightly  acid  reaction  can  be  restored 
in  a  few  minutes  by  the  addition  of  either  citric,  sulphuric, 
acetic,  or  boric  acid,  according  to  the  composition  of  the  bath. 
On  the  other  hand,  when  the  bath  contains  too  much  free  acid, 
it  is  removed  by  the  addition  of  spirits  of  sal  ammoniac,  am- 
monium carbonate,  potash,  or  by  boiling  with  nickel  carbonate, 
the  choice  of  the  remedy  depending  on  the  composition  of  the 
bath. 

The  process  of  electro-nickeling. — Next  to  the  correct  compo- 
sition of  the  bath  and  the  proper  selection  of  the  anodes,  the 
success  of  the  nickeling  process  depends  on  the  thorough  cleans- 
ing of  the  objects  and  the  correct  current- strength. 

The  directions  for  the  removal  of  grease,  etc.,  given  on  p. 
156,  also  apply  to  objects  to  be  nickeled.  In  executing  the 
manipulations,  it  should  always  be  borne  in  mind  that  though 
dirty,  greasy  parts  become  coated  with  nickel,  the  deposit  im- 
mediately peels  off  by  polishing,  because  an  intimate  union  of 
the  deposit  with  the  basis-metal  is  effected  with  only  perfectly 
clean  surfaces.  Touching  the  cleansed  articles  with  the  dry 


DEPOSITION    OF   NICKEL   AND    COBALT.  185 

hand  must  be  strictly  avoided ;  but,  if  large  and  heavy  objects 
have  to  be  handled,  the  hands  should  first  be  freed  from  grease 
by  brushing  with  lime  and  rinsing  in  water,  and  be  kept  wet. 

As  previously  mentioned,  the  cleansed  objects  must  not  be 
exposed  to  the  air,  but  immediately  placed  in  the  bath,  or,  if 
this  is  not  practicable,  be  kept  under  clean  water. 

While  copper  and  its  alloys  (brass,  bronze,  tombac,  German 
silver,  etc.),  as  well  as  iron  and  steel,  are  directly  nickeled,  zinc, 
tin,  Britannia  and  lead  are  generally  first  coppered  or  brassed. 
With  a  suitable  composition  of  the  nickel  bath  and  some  ex- 
perience, the  last-mentioned  metals  may  also  be  directly  nick- 
eled ;  but,  as  a  rule,  previous  coppering  or  brassing  is  preferable, 
the  certainty  and  beauty  of  the  results  being  thereby  consider- 
ably increased. 

By  many  operators  it  is  preferred  to  copper,  iron  and  steel 
articles  before  nickeling,  it  being  claimed  that  by  so  doing 
better  protection  against  rust  is  secured.  However,  compara- 
tive experiments  have  shown  that  with  the  thin  coat  of  copper 
which,  as  a  rule,  is  applied,  this  claim  is  scarcely  tenable,  and 
the  conclusion  has  been  reached  that  a  thick  deposit  of  nickel 
obtained  from  a  bath  of  suitable  composition  protects  the  iron 
from  rust  just  as  long  as  if  it  had  previously  been  slightly  cop- 
pered. It  cannot  be  denied  that  previous  coppering  of  iron 
articles  has  the  advantage,  that  in  case  the  articles  have  not 
been  thoroughly  cleansed,  the  deposit  of  nickel  is  less  liable  to 
peel  off,  because  the  alkaline  copper  bath  completes  the  re- 
moval of  grease,  but  with  objects  carefully  cleansed  according 
to  the  directions  given  on  p.  156,  previous  coppering  is  not 
necessary. 

The  case,  however,  is  different  if  the  copper  deposit  is  pro- 
duced in  order  to  act  as  a  cementing  agent  for  two  nickel  de- 
posits. If,  for  instance,  parts  which  have  previously  been 
nickeled  and  from  which  the  old  deposit  cannot  be  removed 
by  mechanical  means,  are  to  be  re-nickeled,  coppering  is  re- 
quired, because  the  new  deposit  of  nickel  adheres  very  badly 
to  the  old.  Where  articles  are  to  be  protected  as  much  as 


1 86  ELECTRO-DEPOSITION   OF   METALS. 

possible  from  rust,  coppering  is  advisable,  but  the  best  success 
is  attained  by  a  method  different  from  the  one  generally  pur- 
sued. For  nickeling,  for  instance,  parts  of  bicycles  which  are 
exposed  to  all  atmospheric  influences,  the  parts  are  first  pro- 
vided with  a  thick  deposit  of  nickel,  then  with  a  thick  coat  of 
copper,  and  finally,  again  nickeled,  they  thus  being  twice 
nickeled.  It  has  previously  been  mentioned  that  every  de- 
posit is  formed  net-like,  the  meshes  of  the  net  being  larger  or 
smaller,  according  to  the  nature  of  the  metal  deposited.  If 
now  thick  layers  of  two  different  metals  are  deposited  one  on 
the  top  of  the  other,  the  net-lines  of  one  deposit  do  not  con- 
verge into  those  of  the  previous  deposit,  but  are  deposited 
between  them,  thus  consolidating  the  net.  It  will  now  be 
readily  understood  that  by  the  subsequent  polishing  the 
further  consolidation  of  the  deposits  will  be  far  more  complete 
than  when  the  basis-metal  receives  but  one  deposit,  which  is  to 
be  consolidated  by  polishing.  It  is  a  remarkable  fact  that  the 
porosity  of  the  nickel-deposit  varies  if  the  article  is  nickeled  in 
several  baths  of  different  composition.  Thus  denser  deposits 
may  be  obtained  by  suspending  the  articles  in  two  or  three 
baths,  which  proves  that  the  different  resistances  of  the  re- 
spective baths  of  one  and  the  same  metal  exert  an  influence 
upon  the  greater  or  slighter  density  of  the  net. 

The  objects  should  never  be  suspended  in  the  bath  without  cur- 
rent',  the  baths,  with  few  exceptions,  exerting  a  chemical  action 
upon  many  metals  which  is  injurious  to  the  electro-plating  pro- 
cess, and  especially  with  the  nickel  bath  is  it  necessary  to  con- 
nect  the  anode-rods  and  object-rods  before  suspending  the 
articles  in  the  bath. 

The  suitable  current- strength  has  already  been  fully  discussed 
on  p.  89  et  seq.  ("  Electro-plating  Arrangements  in  Particu- 
lar"), and  referring  the  reader  to  that  section  we  may  here  be 
comparatively  brief. 

In  that  section  it  has  been  said  that  the  surfaces  of  objects 
to  be  nickeled  must  be  in  due  proportion  to  the  effective  zinc 
surface  of  the  battery  if  the  latter  be  used  for  generating  the 


DEPOSITION    OF  NICKEL   AND    COBALT.  1 87 

current ;  further,  the  surface  of  anodes  suspended  in  the  bath 
must  be  at  least  equal  to  that  of  the  objects,  though  in  most 
cases  it  is  better  that  it  should  be  larger  On  p.  89  et  seq.,  it 
has  also  been  explained  how,  according  to  circumstances,  the 
elements  have  to  be  coupled  to  a  battery  in  order  to  be  sure  of 
success.  Two  Bunsen  elements,  coupled  one  after  the  other, 
yield  for  nearly  all  nickel  baths  the  electro -motive  force  re- 
quired for  the  reduction  of  the  nickel ;  for  baths  with  great  re- 
sistance it  will,  however,  be  better,  especially  when  the  filling 
of  the  elements  is  no  longer  fresh,  to  couple  three  elements  one 
after  the  other,  and  to  neutralize  a  momentary  excess  of  cur- 
rent by  the  resistance  board. 

An  error  is  frequently  committed  in  nickeling  with  too  strong 
a  current,  the  consequence  being  that  the  deposit  on  the  lower 
portions  of  the  objects  soon  becomes  dull  and  gray-black, 
while  the  upper  portions  are  not  sufficiently  nickeled.  This 
phenomenon,  which  is  due  to  the  reduction  of  the  nickel  with 
a  coarse  grain  in  consequence  of  too  powerful  a  current,  is 
called  burning  or  over-nickeling.  A  further  consequence  of 
nickeling  with  too  strong  a  current  is  that  the  deposit  readily 
peels  off  after  it  reaches  a  certain  thickness.  This  phenomenon 
is  due  to  the  hydrogen  being  condensed  and  retained  by  the 
deposit,  which  is  thereby  prevented  from  acquiring  greater 
thickness. 

Especially  do  those  objects  suspended  on  the  ends  of  the 
rods  nickel  with  great  ease ;  this  evil  can  be  avoided  by  hang- 
ing on  both  ends  of  the  rods  a  strip  of  copper-sheet  about  0.39 
inch  wide,  and  of  a  length  corresponding  to  the  depth  of  the 
bath. 

The  following  criteria  may  serve  for  judging  whether  the 
nickeling  progresses  with  a  correct  current-strength :  In  two  or 
at  the  utmost  three  minutes  all  portions  of  the  objects  must  be 
perceptibly  coated  with  nickel,  but  without  a  violent  evolution 
of  gas  on  the  objects  ;  small  gas  bubbles  rising  without  violence 
and  with  a  certain  regularity  are  an  indication  of  the  operation 
progressing  regularly.  If,  after  two  or  three  minutes,  the  ob- 


1 88  ELECTRO-DEPOSITION    OF   METALS. 

jects  show  no  deposit,  the  current  is  too  weak,  and  in  most  cases 
the  objects  will  have  acquired  dark,  discolored  tones.  In  such 
case  either  a  stronger  current  must  be  introduced  by  means  of 
the  resistance  board,  or,  if  the  entire  volume  of  current  gen- 
erated already  passes  into  the  bath,  the  object-surface  has  to 
be  diminished,  or,  if  this  is  not  desired,  the  battery  must  be 
strengthened  by  adding  more  elements,  or  by  fresh  filling,  etc. 

If,  on  the  other  hand,  a  violent  evolution  of  gas  appears  on 
the  objects,  and  the  latter  are  well  covered  in  a  few  seconds, 
and  the  at  first  white  and  lustrous  nickeling  changes  in  a  few 
minutes  to  a  dull  gray,  the  current  is  too  strong,  and  must  be 
weakened  either  by  the  resistance  board,  or  uncoupling  a  few 
elements,  or  diminishing  the  anode-surface,  or  finally  by  sus- 
pending more  objects  in  the  bath. 

These  criteria  also  apply  to  nickeling  with  the  dynamo. 

The  density  of  current  most  suitable  for  nickeling  copper, 
copper-alloys,  iron  and  steel  is  O.6  ampere  per  15.5  square 
inches,  while  zinc  previously  coppered  requires  1.2  amperes. 

It  will  be  seen  that  in  nickeling  zinc  objects  greater  density  of 
current  and  higher  tension  are  required.  If  the  current  is  not 
of  sufficient  strength,  black  streaks  and  stains  are  formed,  zinc 
is  dissolved  and  the  nickel  bath  spoiled.  These  evils  are 
frequently  complained  of  by  nickel-platers  who  have  not  a  clear 
perception  of  the  prevailing  conditions  (see  polarizing  current). 
A  vigorous  evolution  of  gas  must  take  place  on  the  zinc  ob- 
jects, otherwise  a  serviceable  deposit  will  not  be  obtained. 

In  most  cases  the  electro-plater  will  in  a  few  days  learn 
correctly  to  judge  the  proper  current-strength  by  the  pheno- 
mena presented  by  the  objects,  and  if  he  closely  follows  the 
directions  given  but  few  failures  will  result.  It  may  here  be 
again  repeated  that  the  use  of  a  voltmeter  as  well  as  of  a 
resistance  board  greatly  facilitates  a  correct  estimate  of  the 
proper  current-strength,  and  these  instruments  should  for  the 
sake  of  economy  never  be  omitted  in  fitting  up  an  electro-plat- 
ing plant. 

The  density  of  current  most  suitable  for  nickeling  copper, 


DEPOSITION    OF   NICKEL   AND    COBALT.  189 

copper-alloys,  iron,  and  steel  varies  between  0.4  and  0.8  ampere 
per  15.5  square  inches,  while  zinc,  after  previous  coppering,  re- 
quires 1.3  to  1.5  amperes. 

It  is  in  all  respects  advisable  first  to  cover  the  objects  by 
means  of  a  strong  current,  i.  e.t  to  give  the  first  deposit  rapidly, 
in  order  to  withdraw  the  metals  from  the  action  of  the  bath, 
and  then  finish  the  operation  after  reducing  the  current  to  a 
suitable  strength.  With  a  current  thus  regulated  the  objects 
may  be  allowed  to  remain  in  the  bath  for  hours  and  even  for 
days.  It  is  further  possible  to  nickel  by  weight  and  attain  de- 
posits of  considerable  thickness. 

If  very  thick  deposits  of  nickel  are  desired,  the  objects  must 
be  frequently  turned  in  the  bath,  as  the  lower  portions  nickel 
stronger  than  the  upper;  further,  as  soon  as  the  deposit  ac- 
quires a  dull  bluish  lustre  it  has  to  be  thoroughly  scratch- 
brushed,  in  doing  which,  however,  the  objects  must  not  be 
allowed  to  become  dry.  After  scratch-brushing  it  is  advisable 
to  cleanse  the  deposit  once  more  with  the  lime-brush,  and  after 
rinsing  replace  the  objects  in  the  bath.  If  burnt  places  cannot 
be  brightened  and  smoothed  with  the  scratch-brush,  the  de- 
sired end  is  readily  attained  with  the  assistance  of  emery  paper 
or  pumice. 

For  solid  nickeling  it  suffices  in  most  cases  to  allow  the  ob- 
jects to  remain  in  the  bath  until  the  dull  bluish  lustre  appears, 
this  being  an  indication  that  the  deposit  has  acquired  consider- 
able thickness,  and  will  not  take  a  further  regular  deposit.  If 
such  objects  are  permitted  to  remain  longer  in  the  bath  without 
scratch-brushing,  the  dull  bluish  tone  soon  passes  into  a  dull 
gray,  and  all  the  metal  deposited  in  this  form  must  be  polished 
away  in  order  to  obtain  a  bright  lustre. 

Whether  the  deposit  of  nickel  is  sufficiently  heavy  for  all 
ordinary  demands  is,  according  to  Fontaine,  shown  by  rubbing 
a  nickeled  corner  or  edge  of  the  object  rapidly  and  with  ener- 
getic pressure  upon  a  piece  of  planed  soft  wood  until  it  be- 
comes hot.  The  nickeling  should  bear  this  friction.  This  test 
can  be  recommended  as  perfectly  reliable. 


ELECTRO-DEPOSITION   OF   METALS. 

If  the  objects,  after  having  been  suspended  for  some  time  in 
the  bath,  are  only  partially  nickeled,  it  is  very  likely  due  to  the 
defective  arrangement  of  the  anodes.  This  occurs  chiefly  with 
large  round  objects  and  with  articles  having  deep -depressions 
(cups,  vases,  etc.). 

For  flat  objects  it  is  sufficient  to  suspend  them  between  two 
rows  of  anodes ;  round  objects  with  a  large  diameter  should  be 
quite  surrounded  with  anodes,  and  be  as  nearly  as  possible  equi- 
distant from  them.  This  arrangement  should  especially  not  be 
neglected  where  a  heavy  and  uniform  deposit  of  nickel  is  to  be 
given  to  round  or  half-round  surfaces — for  instance,  large  half- 
round  stereotype  plates  for  revolving  presses. 

While  for  smooth  articles  the  most  suitable  distance  of  the 
anodes  from  the  objects  is  3  ^  to  5  ^  inches,  for  objects  with 
depressions  and  hollows  it  must  be  larger,  if  it  is  not  preferred 
to  make  use  of  the  methods  described  later  on.  However,  a 
deposit  of  a  uniform  thickness  cannot  be  obtained  by  this  means, 
because  the  portions  nearer  to  the  anodes  will  acquire  a  thicker 
deposit  than  the  hollows ;  hence  the  use  of  a  small  hand  anode, 
which  is  connected  by  means  of  a  thin  flexible  wire  with  the 
anode-rod,  and  introduced  into  the  depressions  and  hollows,  is 
to  be  preferred.  This,  of  course,  renders  it  necessary  for  a 
workman  to  stand  alongside  the  bath  and  execute  the  operation 
by  hand ;  but  as  the  small  anode  can  be  brought  within  a  few 
millimetres  of  the  surface  of  the  article,  and  at  this  distance 
slowly  moved  around  it,  a  correspondingly  thick  deposit  is  in  a 
short  time  formed. 

At  any  rate  baths  in  which  objects  with  depressions  and 
hollows  are  to  be  nickeled  must  possess  greater  resistance  than 
baths  for  nickeling  flat  articles,  and  it  is  inexplicable  why  a 
bath  with  a  large  content  of  ammonium  chloride  and  conse- 
quently slight  conducting  resistance  can  be  recommended,  as 
has  been  done,  for  nickeling  hollow  articles. 

In  nickeling  lamp-feet  of  cast-zinc,  the  use  of  the  hand-anode 
can  scarcely  be  avoided  if  the  depressed  portions  also  are  to  be 
provided  with  a  uniformly  good  deposit.  Moreover,  zinc  arti- 


DEPOSITION    OF   NICKEL   AND    COBALT.  191 

cles  form  an  exception  to  the  general  rule  in  so  far  as  by  reason 
of  the  highly  positive  properties  of  zinc  the  resistance  of 
the  bath  may  be  slighter  than  for  baths  for  nickeling  copper 
and  its  alloys,  as  well  as  iron  and  steel. 

Besides  the  above-mentioned  general  rules  for  nickeling,, 
which  also  hold  good  for  other  electro-plating  processes,  the 
following  may  be  given  :  — 

In  suspending  the  objects  in  the  bath,  rub  the  metallic  hooks 
or  wires,  with  which  they  are  secured  to  the  rods,  a  few  times 
to  and  fro  upon  the  rod,  in  order  to  be  sure  that  the  place  of 
contact  is  purely  metallic.  It  is  also  well  to  acquire  the  habit 
of  striking  the  rod  a  gentle  blow  with  the  finger  every  time 
when  suspending  an  object,  the  gas-bubbles  settling  on  the 
articles  becoming  thereby  detached  and  rising  to  the  surface. 
It  is  further  advisable,  before  securing  the  objects  to  the  object- 
rod,  several  times  to  move  them  up  and  down  ;  so  to  say,  shake 
them  beneath  the  fluid,  whereby,  on  the  one  hand,  the  layers 
poorer  in  metal  are  mixed  with  those  richer  in  metal,  and,  on 
the  other,  any  dust  which  may  float  upon  the  bath  and  settle 
on  the  objects  is  removed. 

The  objects  suspended  in  the  bath  should  not  touch  one 
another,  nor  one  surface  cover  another,  and  thus  withdraw  it 
from  the  direct  action  of  the  anode.  In  the  first  case  stains  will 
readily  form  on  the  places  of  contact,  and  in  the  latter  the  cov- 
ered surface  acquires  only  a  slight  deposit.  That  the  objects 
must  not  touch  the  anodes  need  scarcely  be  mentioned. 

Objects  with  depressions  and  hollows  should  be  suspended 
in  the  bath  so  that  the  air  in  the  hollows  can  escape,  which  is 
effected  by  turning  the  depressions  upwards,  or,  if  there  are 
several  depressions  on  opposite  sides,  by  turning  the  articles 
about  after  being  introduced  into  the  bath.  Air-bubbles  re- 
maining in  the  hollows  prevent  contact  with  the  solution,  no 
deposit  being  formed  on  such  places. 

It  remains  to  say  a  few  words  in  regard  to  the  so-called  polar- 
izing phenomena.  In  the  theoretical  part,  it  has  been  shown 
that  by  dipping  two  plates  of  different  metals  in  a  fluid  a  counter 


ELECTRO-DEPOSITION    OF   METALS. 

or polarizing  current 'is  generated,  which  is  the  stronger  the  further 
the  two  metals  are  removed  from  one  another  in  the  series  of 
electro-motive  force,  and  the  more  they  differ  in  their  electrical 
behavior.  If  the  anodes  in  a  nickel  bath  are  of  nickel  and  the 
articles  of  copper,  the  counter-current  will  be  slight,  because 
copper  and  nickel  stand  together  in  the  series  of  electro-motive 
force  (p.  15).  The  counter-current,  however,  becomes  greater 
when  iron  objects  are  hung  in  the  bath,  and  greatest  with  zinc 
surfaces  which  are  to  be  nickeled,  because  zinc,  being  the  most 
electro-positive  metal,  differs  widely  in  its  behavior  from  nickel. 
Now,  since  the  counter-current  flows  in  a  direction  opposite  to 
that  of  the  current  introduced  in  the  bath,  the  latter  is  weakened, 
and  the  more  so  the  stronger  the  counter-current  is.  This  ex- 
plains why  iron  requires  a  stronger  current  for  nickeling  than 
copper  alloys,  and  zinc  a  stronger  one  than  iron. 

Now  it  may  happen  that  the  counter-current  becomes  so 
strong  as  to  entirely  annul  the  effect  of  the  principal  current, 
and  even  to  reverse  the  latter,  the  consequence  being  that,  in 
the  first  case,  the  formation  of  the  deposit  is  interrupted,  and, 
in  the  latter,  that  the  deposit  is  again  destroyed,  and  the  metals 
of  which  the  articles  consist  dissolve  and  contaminate  and  spoil 
the  bath.  To  avoid  this,  a  main  current  must  be  conducted  into 
the  bath,  which,  by  its  sufficiently  large  electro-motive  force, 
can  overcome  the  counter-current,  and  the  consequences  of  the 
reversion  of  the  current  can  be  prevented  by  using  the  galvano- 
meter and  observing  the  deflection  of  its  needle,  which  (accord- 
ing to  p.  95)  in  proper  time  indicates  the  appearance  of  a  re- 
versed current.  Now  if  a  nickel-plater  has  only  a  slight  current 
at  his  disposal,  it  follows  from  the  above  explanation  that  before 
nickeling  the  more  electro-positive  metals,  such  as  iron,  tin, 
zinc,  it  is  best  first  to  copper  them,  and  thereby  annul  the  action 
of  these  metallic  surfaces  as  regards  the  formation  of  the  counter- 
current. 

It  happens  comparatively  seldom  that  the  counter-current 
becomes  so  strong  as  to  destroy  the  deposits  formed,  because 
for  nickeling  powerful  Bunsen  elements,  with  two  acids  or 


f  ' 

DEPOSITION   OF  NICKEL  AND    COBALT.  193 

dynamo-electric  machines  with  at  least  4  volts'  tension,  are 
generally  used ;  it  is,  however,  well  to  acquaint  the  operator 
with  all  possible  contingencies,  and  to  explain  the  reason  why 
the  articles  are  preferably  covered  with  a  strong  current. 
Sprague  recommends  an  initial  current  of  5  volts'  tension,  but 
in  most  cases  one  of  3.5  volts  suffices  for  nickeling  iron  and 
copper  alloys. 

Nickeling  en  masse  of  small  and  cheap  objects. — This  is 
effected  by  stringing  the  objects,  if  feasible,  upon  a  copper  wire, 
and  placing  a  large  glass  bead  between  every  two  objects,  to 
prevent  the  surfaces  from  sticking  together  in  the  bath.  Such 
objects  being  generally  only  slightly  nickeled,  it  suffices  to 
allow  them  to  remain  for  a  few  minutes  only  in  the  bath  with  a 
strong  current,  it  being  advisable  to  diligently  shake  the 
bundles  in  order  to  effect  a  change  of  position  of  the  objects 
and  prevent  their  touching  one  another,  notwithstanding  the 
glass  bead  placed  between  them. 

Very  small  objects,  such  as  rivets,  pins,  etc.,  which  cannot  be 
strung  upon  wire,  are  nickeled  in  a  stoneware  dipping  basket. 
To  the  bottom  of  the  dipping  basket  is  secured  a  copper  or 
brass  wire,  which  is  connected  with  the  object-rod,  and  the 
articles,  not  too  many  at  a  time,  are  then  placed  in  the  basket. 
During  the  operation  the  articles  must  be  constantly  shaken, 
and  as  nickel  baths,  as  a  rule,  do  not  conduct  sufficiently  well 
to  properly  nickel  the  objects  in  the  basket,  it  is  advisable  to 
hold  with  one  hand  an  anode  connected  by  a  flexible  wire  with 
the  anode-rod  in  the  basket  while  the  other  hand  holds  the 
sieve  (Fig.  107)  and  constantly  shakes  and  turns  it.  For 
nickeling  in  the  dipping  basket  it  is  further  advisable  to  heat 
the  nickel  bath. 

In  place  of  a  stoneware  dipping  basket  one  of  brass  wire  to 
which  are  soldered  two  copper  wires  for  suspending  it  to  the 
object-rod  may  preferably  be  used.  From  the  soldered  places 
a  few  copper  wires  extend  to  the  bottom  of  the  basket.  To 
prevent  an  unnecessary  deposit  of  nickel  upon  the  basket  the 
latter  is  coated  with  asphalt  varnish  and  at  a  distance  of  about 
13 


194 


ELECTRO-DEPOSITION    OF   METALS. 


2^  to  three  inches  below  the  basket  an  anode  is  arranged  in 
horizontal  position,  while  with  one  hand  a  hand-anode  is  held 
over  the  small  articles  in  the  basket.  By  this  arrangement  a 
thicker  deposit  is  more  quickly  obtained,  especially  if  with  the 
other  hand  the  articles  are  incessantly  stirred  by  means  of  a 
glass  or  wooden  rod. 

O 

Warren  has  described  a  solution  of  nickel  and  one  of 
cobalt  which  can  be  decomposed  in  a  simple  cell  apparatus. 
With  the  nickel  solution,  which  was  prepared  by  dissolving  100 

FIG.  107. 


parts  by  weight  of  nickel  chloride  in  as  little  water  as  possible 
and  mixing  with  a  concentrated  solution  of  500  parts  of 
Rochelle  salts,  no  satisfactory  results  could  be  obtained ;  the 
cobalt  solution  however  yielded  good  results,  and  would  seem 
to  be  suitable  for  electro-plating  small  objects  en  masse.  It  will 
be  further  discussed  under  "  Cobalting." 

Stripping  nickeled  articles. — Defective  nickeling  must,  as  a 
rule,  be  completely  removed  before  the  objects  can  be  re- 
nickeled,  since  the  second  deposit  adheres  badly  to  the  previous 
ore,  especially  if  the  latter  has  become  dry.  The  removal  of  a 


DEPOSITION    OF   NICKEL   AND    COBALT.  195 

nickel-deposit  is  in  most  cases  a  disagreeable  labor,  which,  how- 
ever, can  most  assuredly  be  saved  if  the  utmost  care  and  pains- 
taking cleanliness  are  observed  in  freeing  the  articles  from  grease 
and  in  regulating  the  current.  For  the  removal  of  the  nickel 
coating  the  following  stripping  acid,  which  may  be  used  either 
cold  or  tepid,  has  been  recommended :  Sulphuric  acid  of  66° 
Be,  4  Ibs. ;  nitric  acid  of  40  Be.,  i  Ib. ;  water  about  I  pint.  First 
put  the  water  in  a  stoneware  jar  and  cautiously  add,  a  little  at  a 
time,  the  sulphuric  acid,  since  considerable  heat  is  generated 
when  this  acid  is  mixed  with  water.  When  the  entire  quantity 
of  sulphuric  acid  has  been  added,  pour  in  the  nitric  acid,  when 
the  bath  is  ready  for  use.  In  making  up  the  stripping  bath, 
the  proportion  of  the  acids  may  be  varied,  but  the  foregoing 
will  be  found  to  answer  every  purpose.  An  addition  of  8  ozs. 
of  potassium  nitrate  to  the  bath  has  also  been  recommended. 

When  stripping  nickel-plated  articles  in  the  above  bath  it  is 
necessary  to  watch  the  operation  attentively,  since  some  articles 
are  very  lightly  coated  and  a  momentary  dip  is  frequently  suf- 
ficient to  deprive  them  of  their  nickel.  Other  articles  which 
having  been  thoroughly  well  nickeled,  require  from  some  acci- 
dental cause  to  be  stripped  and  re-nickeled,  will  need  immer- 
sion for  several  minutes — indeed  well-nickeled  articles  may  oc- 
cupy nearly  half  an  hour  in  stripping  before  the  underlying  sur- 
face is  entirely  freed  from  nickel.  The  operation  of  stripping 
should  be  conducted  in  the  open  air,  or  in  a  fire-place,  so  that 
the  acid  fumes,  which  are  very  pernicious,  can  escape  freely. 
The  articles  should  be  attached  to  a  stout  copper  wire,  and 
after  a  few  moments'  immersion  should  be  removed  from  the 
bath  to  ascertain  how  the  stripping  progresses ;  and  the  moment 
it  is  found  that  the  nickel  has  quite  disappeared  from  every 
part,  the  article  must  be  plunged  into  clean  cold  water.  It  is 
absolutely  necessary  that  the  work  should  not  remain  in  the 
stripping  solution  one  instant  after  the  nickel  is  removed. 
When  the  stripping  has  been  properly  effected  the  underlying 
metal  exhibits  a  bright,  smooth  surface,  giving  little  evidence  of 
the  mixture  having  acted  upon  it. 


196  ELECTRO-DEPOSITION   OF   METALS. 

Many  platers,  however,  prefer  to  remove  the  nickel-coating 
mechanically  by  brushing  with  emery.  From  depressions  as 
much  as  possible  is  removed  with  the  brush,  after  which  the 
object  is  freed  from  grease  and  pickled,  and  coppered  before 
nickeling.  In  this  case  the  layer  of  copper  serves  for  cement- 
ing together  the  old  and  new  deposits,  and  there  will  be  no 
danger  of  the  new  deposits  peeling  off  in  polishing. 

It  has  also  been  proposed  to  remove  the  nickel  from  the  articles 
by  means  of  the  battery  or  dynamo-machine  by  making  them 
the  anodes  in  a  nickel  bath ;  but  in  this  case  a  separate  solution 
should  be  employed  for  the  purpose. 

As  a  remedy  against  the  yellowish  tone  of  the  nickeling,  Pfan- 
hauser  recommends  suspending  the  nickeled  articles,  immedi- 
ately after  taking  them  from  the  nickel  bath,  as  anodes  in  a 
nickel  bath  acidulated  with  citric  or  hydrochloric  acid,  a  piece 
of  sheet  nickel  serving  as  the  cathode,  and  to  allow  the  current 
to  act  for  a  few  seconds.  It  is  claimed  that  thereby  the  basic 
nickel  salts  separated  together  with  the  nickel,  and  to  which, 
according  to  Pfanhauser,  the  yellowish  tinge  is  due,  are  dissolved 
and  the  nickeling  will  show  a  pure  white  tone. 

The  following  is  a  brief  resume  of  the  principal  pheno- 
mena which  may  occur  in  nickeling,  as  well  as  the  means  of 
avoiding  them : 

1.  The  articles  do  not  become  coated  with  nickel,  but  acquire 
discolored,  generally  darker  tones.     Reasons:  The   current  fs 
either  too  feeble  to  effect  the  reduction  of  nickel,  and  the  colora- 
iton  is  in  consequence  of  the  chemical  action  of  the  nickel  solu- 
tion upon  the  metals   constituting  the  objects.     Remedy:  In- 
crease the  current  or  diminish  the  area  of  suspended  objects ; 
also  examine  whether  the  current  actually  passes  into  the  bath, 
otherwise  clean  the  places  of  contact. 

2.  A  deposition  of  nickel  takes  place,  but  it  is  dark  or  spotted 
or  marbled,  even  with  a  sufficiently  strong  current.     Reasons: 
The  bath  is  either  alkaline,  which  has  to  be  ascertained  by  lit- 
mus paper,  and,  if  so,  the  slightly  acid  reaction  of  the  bath  has 
to  be  restored  by  the  addition  of  a  suitable  acid ;  or,  the  bath  is 


^ 


DEPOSITION   OF  NICKEL   AND    COBALT.  197 

too  concentrated,  in  which  case  a  separation  of  crystals  will  be 
observed — this  is  remedied  by  diluting  with  water;  or,  the 
nickel  solution  is  very  poor  in  metal,  which  can  be  remedied  by 
the  addition  of  nickel  salt ;  it  should  also  be  tested  as  to  the  ad- 
mixture of  copper,  the  production  of  dark  tones  being  fre- 
quently due  to  this — in  this  case  the  bath  is  allowed  to  work 
for  some  time,  and  if  the  content  of  copper  is  inconsiderable  a 
white  deposit  will  soon  be  obtained ;  or,  the  cleaning  and  pickl- 
ing of  the  articles  have  not  been  thoroughly  done,  which  is 
remedied  by  again  cleaning  them ;  or,  the  conducting  power  of 
the  bath  is  insufficient,  which  is  remedied  by  the  addition  of  a 
suitable  conducting  salt. 

When  freshly  prepared  baths  yield  dark  nickeling,   it  can 
generally  be  remedied  by  working  the  bath  two  or  three  hours. 

3.  A  yellowish  tinge  of  the  nickeling.     Reasons:  See  under 
2 ;  or,  with  cast-iron  an  insufficient  metatlic  surface,  which  is 
remedied    by    repeating    the    scratch-brushing :   or,  unsuitable 
composition  of  the  bath. 

4.  The  objects  rapidly  acquire  a  white  deposit  of  nickel,  but 
the  color  soon  changes  to  dull  gray-black,   especially  on  the 
lower  edges  and  corners.    Reason:  Too  strong  a  current.    Rem- 
edies: Regulating  the  current,  or  hanging  in  more  objects,  or 
uncoupling  elements.     Frequent  turning  of  the  articles. 

5.  The  nickeling  is  white,  but  readily  peels  off  by  scratching 
with  the  finger-nail  or  by  the  action  of   the  polishing  wheel. 
Reasons:  The  current  is  too  strong,  which  is  remedied  as  under 
4 ;   or,  the  bath  is  too  acid — this  is  remedied  by  the  addition 
of  spirit  of  sal  ammoniac,  potassium  carbonate,  or  nickel  car- 
bonate, according  to  the  composition  of  the  bath :  or,  insuffici- 
ent cleaning  and  pickling,  which  is  remedied  by  thorough  clean- 
ing after  removing  the  defective  deposit,  or,  if  it  cannot  be  en- 
tirely removed,  coppering. 

6.  Though  nickeling  may  proceed  in  a  regular  manner,  some 
places  remain  free  from  deposit.     Reasons:  Either  the  surfaces 
of  some  of  the  objects  touch  one  another,  or  air  bubbles  are  in- 
closed   in    cavities ;    or,    faulty    arrangement    of    the    anodes. 
Remedy:  Removal  of  the  causes. 


198  ELECTRO-DEPOSITION   OF   METALS. 

7.  The  deposit  appears  with  small  holes.     Reason:  A  deposit 
of  particles  of  dust  upon  the  objects.     Remedy:  Remove  the 
dust  from  the  surface.     When  there  is  a  general  turbidity  of  the 
bath  in  consequence  of   alkalinity,  add  the  most  suitable  acid, 
and   boil   and   filter   the  bath ;    or,  insufficient  removal  of    gas 
bubbles  from  the  objects.     Remedy:  Shake  the  object-rods  by 
blows  with  the  finger. 

8.  Deposition  takes  place  promptly  upon  the  portions  of  the 
objects  next  to  the  anodes,  while  deeper  portions  remain  free 
from  nickel  or  become  black ;  or  the  portions  covered  by  the 
suspending  wire   show   dark  lines.     Reason:  Insufficient  con- 
ducting power  of  the  bath.     With  large  depressions  this  cannot 
be  remedied  by  the  addition  of  a  suitable  conducting  salt,  but 
requires  treatment  with  the  hand-anode. 

Refreshing  nickel  baths. — According  to  their  composition,  the 
amount  of  work  performed,  and  the  anodes  used,  the  baths  will 
in  a  shorter  of  longer  time  require  certain  additions  in  order  to 
keep  their  action  constant.  By  "  refreshing"  is  not  understood 
the  small  addition  of  acid  or  alkali  from  time  to  time  required 
for  restoring  the  original  reaction  of  the  baths,  but  additions 
intended  to  increase  the  metallic  content  and  diminished  con- 
ductivity. 

The  metallic  content  is  increased  by  boiling  the  bath  with 
some  of  the  nickel  salt  used  in  its  preparation,  while  the  con- 
ductivity is  improved  by  adding,  at  the  same  time,  so  much 
conducting  salt  as  is  necessary  to  restore  the  electro-motive 
force  originally  required.  Nothing  definite  can,  of  course,  be 
said  in  regard  to  the  quantity  of  such  additions,  it  being  advis- 
able to  observe  their  effect  on  a  small  portion  of  the  bath,  so  as 
to  be  sure  not  to  spoil  the  entire  bath. 

Nickel  baths  bear,  as  a  rule,  refreshing  several  times,  but  as 
in  the  course  of  time  they  take  up  impurities,  even  when  the 
greatest  care  is  exercised,  it  is  best  to  refresh  them  at  the 
utmost  twice,  and  then  to  renew  them  entirely. 

The  treatment  of  the  articles  after  nickeling  as  well  as  after 
all  electro-plating  processes  has  already  been  described  and 


DEPOSITION    OF   NICKEL   AND    COBALT.  1 99 

it  is  only  necessary  here  to  refer  again  to  the  fact  that  with 
articles  of  iron  and  steel,  immersion  in  boiling  water  before 
drying  in  saw-dust  is  absolutely  necessary,  and  subsequent  dry- 
ing in  a  drying  chamber  is  also  a  great  safeguard  as  regards 
stability  and  protection  against  rust. 

Nickel  deposits  are  polished  upon  felt  disks  or  bobs  of  cloth, 
muslin,  or  flannel,  with  the  use  of  Vienna  lime,  rouge,  etc.  (See 
"Polishing,"  page  137.)  Sharp  edges,  corners,  and  raised 
portions  should  be  held  only  with  slight  pressure  against  the 
polishing  wheels,  they  being  more  strongly  attacked  by  them 
than  flat  surfaces.  Knife-blades  and  surgical  instruments  with 
sharp  edges  require  special  care  in  polishing,  which  will  be  re- 
ferred to  later  on. 

After  polishing,  the  nickeled  objects,  especially  those  with 
depressions,  have  to  be  freed  from  polishing  dirt  by  brushing 
with  hot  soap-water  or  dilute  hot  caustic  lye,  then  rinsed  in  hot 
water  and  dried  in  clean,  fine  saw-dust. 

Objects  which  are  not  required  to  be  polished,  but  left  dead, 
that  is,  just  as  they  come  out  of  the  nickel  bath,  should  be  taken 
from  the  bath  one  at  a  time,  and  at  once  plunged  into  perfectly 
clean  hot  water  for  a  few  moments,  and  then  placed  aside  to 
dry  spontaneously.  Dead  nickel  being  very  readily  stained  or 
soiled,  even  when  touched  with  clean  hands,  the  work  should  be 
handled  as  little  as  possible. 

Nickeling  sheet  zinc. — The  nickeling  of  sheet  zinc  has  been 
surrounded  with  a  great  deal  of  mystery  by  those  engaged  in 
its  manufacture,  which  may,  perhaps,  be  excusable  on  the 
ground  that  there  is  scarcely  another  branch  of  the  electro- 
plating industry  in  which  experience  had  to  be  acquired  at  the 
sacrifice  of  so  much  money  and  time  as  in  this.  Nevertheless 
the  nickeling  of  sheet  zinc  makes  no  greater  demand  on  the  intel- 
ligence of  the  operator  than  any  other  electro-plating  process, 
it  requiring  only  an  accurate  consideration  of  the  relations  of 
the  electric  behavior  of  zinc  towards  nickel •;  consequently,  a 
knowledge  of  the  strength  of  the  counter-current  and  of  the 
chemical  behavior  of  zinc  towards  the  nickel  solution,  which 


200  ELECTRO-DEPOSITION    OF   METALS. 

may  readily  dissolve  the  zinc ;  further,  a  correct  estimation  of 
the  current-intensity  required  for  a  determined  zinc  surface,  as 
well  as  of  the  proper  anode-surface,  and  the  most  suitable  com- 
position and  treatment  of  the  nickel  baths. 

With  due  observation  of  these  relations,  the  nickeling  of  sheet 
zinc  is  accomplished  as  readily  as  that  of  other  metals ;  and  the 
proposals  to  first  cover  the  sheets  in  a  bath  with  a  strong  cur- 
rent, and  finish  nickeling  with  a  weaker  current,  or  to  amalga- 
mate the  zinc  before  nickeling,  need  not  be  considered. 

Below  the  condititions  required  for  nickeling  sheet  zinc,  and 
the  execution  of  the  process  itself,  together  with  the  pre- 
liminary and  final  polishing  of  the  sheets,  will  be  found  fully 
described. 

The  preliminary  grinding  or  polishing  is  effected  upon  broad 
cloth  disks  (buffs)  formed  of  separate  pieces  of  cloth.  The 
polishing  lathes  run  with  their  points  in  movable  bearings  se- 
cured in  a  hanging  cast-iron  frame  by  a  set  screw  and  safety 
keys,  or  preferably  as  shown  in  Fig.  94,  p.  140,  since  with  this 
construction  an  injury  to  the  grinder  by  the  lathe  jumping  out 
is  impossible. 

The  buffs,  when  new,  have  on  an  average  a  diameter  of  12  to 
1 6  inches,  and  a  width  of  5^  to  8  inches;  the  principal  point 
in  the  construction  of  these  bobs  is  uniform  weight  on  all  sides, 
the  quiet  running  and  the  possibility  of  a  good  polish  without 
great  exertion  depending  on  this.  Bobs  not  well  balanced  run 
unsteadily  and  jump,  thereby  producing  fine  scratches  upon  the 
sheet.  The  bobs  are  constructed  as  follows :  A  square  piece 
of  cloth  is  folded  fourfold  and  the  closed  point  cut  off  with  a 
pair  of  scissors,  so  that  on  unfolding  the  cloth  the  hole  produced 
by  the  cut  is  exactly  in  the  centre  of  the  cloth  disk;  according 
to  the  diameter  of  the  spindle  more  or  less  is  cut  away,  but  in 
every  case  just  sufficient  that  the  piece  of  cloth  can  be  conven- 
iently pushed  upon  the  spindle.  The  latter,  which  is  provided 
with  a  pulley  and  a  hoop  against  which  the  pieces  of  cloth  fix 
themselves,  as  well  as  with  a  nut  and  screw  for  securing  them,  is 
vertically  fasiened  in  a  vise,  and  the  separate  pieces  of  cloth  are 


DEPOSITION    OF   NICKEL   AND    COBALT. 


201 


FIG.  1 08. 


pushed  upon  it  so  that  the  second  piece  placed  in  position  forms 

an  angle  of  about  30°    (Fig.   108)  with  the 

first,    the    operation   being  thus   continued 

until  the  bob  has  the  desired  width.     Next 

a  small,  but  very  strong  iron  disk  is  laid 

upon  the  cloth  disk,  and  the  separate  pieces 

are  pressed  together  as  firmly  as  possible 

with  the  screw.     The  spindle  is  then  placed 

in  the  bearings,  and  after  adjusting  the  belt 

upon  the  pullley  the  bob  is  revolved,  a  sharp 

knife  being  held  against  it  to  remove  the  projecting  corners. 

In  polishing  sheet  zinc  the  bobs  make  2400  to  3000  revolutions 

per  minute,  according  to  whether  finely  rolled  or  rougher  sheets 

are  to  be  polished. 

For  the  purpose  of  polishing  or  grinding,  the  operator  places 
the  sheet  upon  a  support  of  hard  wood  of  the  same  size  and 
form  as  the  sheet,  and  grasps  the  two  corners  of  the  sheet 
nearest  to  his  body,  together  with  the  support,  with  the  hands, 
applying  with  the  balls  of  the  hands,  the  necessary  pressure  to 
hold  the  sheet  upon  the  support.  The  lower  half  of  the  sheet, 
that  furthest  from  the  body,  rests  upon  the  knees  of  the  opera- 
tor, and  with  them  he  presses  the  sheet  against  the  polishing 
disk,  constantly  moving  at  the  same  time,  and  at  not  too  slow 
a  rate,  the  knees  from  the  right  to  the  left,  then  from  the  left  to 
the  right,  and  so  on.  Previous  to  polishing,  a  streak  of  oil 
about  2  inches  wide  is  applied  by  means  of  a  brush  to  the 
centre  of  the  sheet  in  the  visual  line  of  the  operator,  and  the 
revolving  bob  is  impregnated  with  Vienna  lime  by  holding  a 
large  piece  of  it  against  it,  when  polishing  of  the  lower  portion 
of  the  sheet  begins.  When  about  |  of  the  surface  has  thus 
been  polished,  the  sheet  is  turned  round  and  the  remaining 
portion  subjected  to  the  same  process.  The  sheet  is  then 
closely  inspected  to  see  whether  there  are  still  dirty  or  dull 
places,  and,  if  such  be  the  case,  it  is  polished  once  more  after 
moistening  it  with  some  oil  and  again  impregnating  the  bob 
with  Vienna  lime.  The  sheet  being  sufficiently  polished,  the 


202 


ELECTRO-DEPOSITION    OF   METALS. 


oil  and  polishing  dirt  are  removed  by  dry  polishing,  after  pro- 
viding the  bob  with  sufficient  Vienna  lime,  so  that  the  sheets 
when  finished  show  no  streaks  of  dirt  or  oil. 

Self -acting  sheet  polishing  machines  have  been  constructed  by 
Dr.  Sackur,  F.  Rauber,  Eliachoff,  and  others.  Such  machines 
give  a  very  good  polish,  but  have  the  disadvantage  that  thin 
sheets  when  polished  upon  them  become  wrinkled  or  wind  up 
on  the  polishing  roller. 

In  order  to  explain  the  principle  upon  which  these  machines 
are  constructed,  a  description  of  F.  Rauber's  sheet  grinding  and 
polishing  machine  is  given.  With  this  machine  metallic  sheets 
of  any  length  can  be  polished ;  by  the  simultaneous  lateral  and 
longitudinal  motion  of  the  sheets  a  faultless  polish  is  obtained, 
streaks- and  scratches  being  especially  avoided. 

FIG.  109. 


The  machine  essentially  consists  of  the  gearing  A  and  the 
actual  polishing  machine  B,  Figs.  109,  no,  in.  The  gearing 
A  consists  of  the  two  standards  a  a,  the  shaft  b,  a  fast  and  loose 
pulley,  c  c,  the  large  driving-wheel  d,  a  small  driving-wheel,  e, 
and  the  eccentric/. 

The  polishing  machine  B  consists  of  the  wooden  frame  g  with 
wooden  plate  h,  the  two  standards  i  i,  the  polishing  roller  £, 
the  iron  counter-roller  /,  the  expanding  contrivance  m,  which  is 


DEPOSITION   OF  NICKEL   AND    COBALT. 


203 


«»    *> 


IB— 


~y.-.^hr.-.-.:.^fl 


m 


1 


- 


effected  by  means  of  three  spiral  springs,  the  gearing  n  with  the 
rope-drum  o,  the  rope  with  the  tongs g,  and  the  shaking  arrange- 
ment x. 


204  ELECTRO-DEPOSITION   OF   METALS. 

The  machine  is  set  in  motion  by  the  engaging  coupling  x  on 
the  gearing  A.  The  shaft  of  the  gearing  makes  about  200  revo- 
lutions per  minute,  and  the  polishing  roller  k  is  revolved  by  a 
belt  from  the  driving-wheel  d.  At  the  same  time  the  gearing 
n  is  set  in  motion  by  a  belt  from  the  driving-wheel  e,  in  conse- 
quence of  which  the  rope  is  wound  upon  the  drum  o,  and  the 
tongs  on  the  rope  draw  the  sheet  to  be  polished  under  the 
polishing  roller.  If  the  sheet  is  to  go  back,  the  rope-drum  o  is 
disengaged  by  means  of  the  coupling  yt  and  the  polishing 
roller  k,  which  moves  lightly  upon  the  counter-roller  /,  draws 
the  sheet  back.  To  prevent  the  sheet  from  jumping  back,  the 
brake  r  is  provided  on  the  rope-drum  o.  By  the  treadle  r^  the 
workman  is  enabled  to  transport  the  sheet  slowly  or  rapidly,  as 
may  be  required.  To  move  the  sheet  forward,  the  rope-drum  o 
is  again  engaged.  The  lateral  motion  of  the  sheet  is  effected 
by  the  shaking  contrivance  x. 

From  the  eccentric/,  of  the  gearing  A,  the  slide  rod  t  is  con- 
nected with  the  joint  lever  x  and  the  latter  by  the  pin  s  with  the 
table  plate  h,  whereby  the  latter  when  the  machine  is  running 
is  moved  to  the  sides. 

The  centre  of  motion  of  the  table  plate  is  upon  the  pin  v.  To 
regulate  the  pressure  of  the  sheet  against  the  polishing  roller, 
the  expanding  arrangement  m  is  placed  under  the  table  plate  h. 
It  consists  of  three  vertical  bolts  with  spiral,  springs,  each  of 
which  can  be  screwed  up  and  down  by  a  nut. 

To  facilitate  the  lateral  motion  of  the  table  plate  h,  the  bolts 
of  the  expanding  contrivance  m  are  provided  with  rolls  which 
press  against  the  plate.  If  the  tension  is  sufficient  and  a  sheet 
is  to  be  introduced,  it  is  only  necessary  to  draw  the  table  plate 
down  by  means  of  the  treadle  w,  to  push  the  sheet  under  the 
polishing  roll  k,  and  to  engage  the  tongs  g.  In  front  of  the 
gearing  A  is  a  table  for  the  reception  of  the  sheet,  as  shown  in 
the  illustration. 

The  sheets  are  best  freed  from  grease  in  two  operations,  first 
dry  and  then  wet.  For  the  dry  process  use  a  very  soft  piece  of 
cloth,  and,  after  dipping  it  in  Vienna  lime  very  finely  pulverized 


DEPOSITION    OF   NICKEL   AND    COBALT.  2O5 

and  passed  through  a  hair  sieve,  rub  over  the  sheet  in  the  di- 
rection at  a  right  angle  to  the  polishing  streaks,  applying  a  very 
gentle  pressure.  For  the  wet  process  dip  a  wet  piece  of  cloth  or 
a  soft  sponge  free  from  sand  into  a  paste  of  impalpable  Vienna 
lime,  whiting,  and  water,  and  go  carefully  over  the  sheet  so  that 
no  place  remains  untouched.  Then  rinse  the  sheet  under  a 
powerful  jet  of  water,  best  under  a  rose,  being  especially  care- 
ful to  remove  all  the  lirne,  going  over  the  sheet,  if  necessary, 
with  a  soft  wet  rag  and  observing  whether  all  portions  appear 
evenly  moistened.  If  such  be  the  case,  the  cleaning  is  com- 
plete, otherwise  the  sheet  has  to  be  treated  once  more  with  lime. 

If  the  sheets  are  to  be  nickeled  on  only  one  side,  two  of  them 
are  placed  together  with  their  unpolished  sides  and  fastened  on 
the  two  upper  corners  with  binding  screws  to  which  is  soldered 
a  copper  strip  about  0.39  inch  wide,  by  which  they  are  sus- 
pended to  the  conducting  rods.  Plating  is  then  at  once  pro- 
ceeded with  without  allowing  the  sheets  to  remain  exposed  to 
the  air  longer  than  is  absolutely  necessary.  Special  care  must 
be  had  that  the  lime  does  not  dry,  as  this  would  produce  stains. 

Some  manufacturers  nickel  the  cleansed  sheets  without  previ- 
ous coppering  or  brassing,  and  claim  special  advantages  for 
such  direct  nickeling.  This  may  be  done  with  a  bath  of  nickel 
sulphate  and  potassium  citrate  without  or  with  a  greater  or 
smaller  addition  of  sal  ammoniac,  according  to  the  area  to  be 
nickeled  and  the  intensity  of  current  at  disposal.  However, 
sheet  zinc  directly  nickeled  does  not  show  the  warm  full  tone  of 
sheets  previously  coppered  or  brassed ;  besides,  direct  nickel- 
ing requires  a  far  more  powerful  current,  so  that  it  is  not  even 
more  economical. 

For  the  nickeling  process  itself,  it  is  indifferent  whether  the 
sheets  are  previously  coppered  or  brassed,  but  the  choice  be- 
tween the  two  is  controlled  by  a  few  phenomena  which  must  be 
mentioned.  The  nickel  deposit  upon  brassed  sheets  shows  a 
decidedly  whiter  tone  than  that  upon  coppered  sheets,  and 
brassing  would  deserve  the  preference  if  this  process  did  not 
require  extraordinarily  great  care  in  the  proper  treatment  of  the 


206  ELECTRO-DEPOSITION   OF   METALS. 

bath,  the  nickel  deposit  readily  peeling  off  generally  in  the  bath 
itself,  which  seldom  or  never  occurs  with  coppered  sheet,  and 
then  may  generally  be  considered  due  to  insufficient  cleaning 
or  other  defective  manipulation. 

This  peeling  off  of  the  nickel  deposit  may  be  prevented  by 
giving  due  consideration  to  the  conditions,  and  avoiding,  on  the 
one  hand,  too  large  an  excess  of  potassium  cyanide  in  the  brass 
bath,  and,  on  the  other,  by  regulating  the  current  so  that  no 
pale  yellow  or  greenish  brass  is  precipitated.  Since  nickeling 
with  a  strong  current  requires  only  a  few  minutes  for  a  deposit 
of  sufficient  thickness  capable  of  bearing  polishing,  it  is  gener- 
ally desired  to  brass  the  sheets  at  the  same  time,  so  that  the 
operation  may  proceed  rapidly  and  continuously.  To  do  this, 
a  very  powerful  current  has  to  be  conducted  into  the  brass  bath, 
the  result  being  that  a  deposit  with  a  larger  content  of  zinc  and 
a  correspondingly  lighter  color  is  formed,  but  also  with  a 
coarser,  less  adherent  structure,  and  this  is  the  principal  reason 
why  the  nickel  deposit,  together  with  the  brass  deposit,  peels 
off.  To  avoid  this,  the  brassing  must  be  done  with  a  current 
so  regulated  that  the  deposit  separates  uniformly,  adheres  firmly, 
and  is  not  porous,  the  correct  progress  of  the  operation  being 
recognized  by  the  color  being  more  like  tombac,  and  not  pale 
yellow  or  greenish.  Where  brassing  has  to  be  done  quickly 
the  content  of  copper  in  the  brass  bath  must  be  increased  to 
such  an  extent  that  a  powerful  current  produces  a  deposit  of 
the  above-mentioned  color,  and,  hence,  too  large  an  excess  of 
potassium  cyanide  must  be  strictly  avoided. 

It  will  be  seen  that  the  brassing  requires  a  certain  attention 
which  is  not  necessary  in  coppering,  and  therefore  the  latter  is 
to  be  preferred. 

For  coppering  one  of  the  baths,  III.  or  V.,  given  under  "  Cop- 
pering "  serves,  to  which,  for  this  special  purpose,  more  potas- 
sium cyanide  may  be  added.  The  sheets  should  remain  in  this 
bath  no  longer  than  required  to  uniformly  coat  them  with  a 
beautiful  red  layer  of  copper,  and  under  no  circumstances  must 
they  be  allowed  to  remain  until  the  coppering  commences  to 


DEPOSITION    OF   NICKEL   AND    COBALT.  2O/ 

become  dull  or  even  discolored ;  and  they  should  come  from 
the  bath  with  a  full  or  at  least  half  lustre.  When  taken  from 
the  copper  bath  the  sheets  are  thoroughly  rinsed  in  a  large 
water  reservoir,  the  contents  of  which  must  be  frequently  re- 
newed, care  being  had  to  remove  any  copper  solution  adhering 
to  the  unpolished  sides  which  are  not  to  be  nickeled,  since  that 
would  soon  spoil  the  nickel  bath.  The  sheets  are  then  immedi- 
ately brought  into  the  nickel  bath,  it  being  best  to  suspend  two, 
three,  or  four  plates  at  the  same  time,  to  prevent  one  from  being 
more  thickly  nickeled  than  the  other,  and  take  them  out  the 
same  way.  In  suspending  the  plates  in  the  bath,  care  should 
be  had  to  bring  them  as  soon  as  possible  in  contact  with  the 
conducting  rod,  a  neglect  of  this  rule  being  apt  to  produce 
blackish  streaks  and  stains. 

Every  separate  nickel  bath  in  which  sheets  are  to  be  nickeled 
must  be  fed  with  the  full  current  of  a  dynamo-machine,  one  of 
250  to  300  amperes  with  4  volts'  tension  being  generally  used. 
According  to  the  number  of  sheets,  generally  6  to  8,  each  20x20 
inches,  to  be  nickeled,  the  dimensions  of  the  vats  are  as  follows  : 
63  inches  long,  15^  inches  wide,  and  255^  inches  deep,  or,  83 
inches  long,  15^  inches  wide,  and  25^  inches  deep.  One  to 
two  minutes  suffice  to  give  6  sheets  a  sufficiently  thick  deposit  of 
nickel  with  a  dynamo-machine  of  the  above-mentioned  capacity, 
and  2  to  3  minutes  for  eight  sheets ;  and  it  may  be  accepted  as 
a  rule  that,  with  a  bath  of  good  conductivity,  a  density  of  cur- 
rent of  from  1.4  to  1.5  amperes  and  5  volts'  tension  is  required 
per  15.5  square  inches  of  zinc  surface  for  the  solid  nickeling  of 
the  sheets.  For  nickeling  zinc  in  baths  conducting  with  diffi- 
culty, for  instance,  a  simple  solution  of  sulphate  of  nickel  and 
ammonia  without  the  addition  of  conducting  salts,  or  in  baths 
containing  boric  acid,  1.3  to  1.4  amperes  and  6  to  7  volts,  must 
be  allowed  per  1.55  square  inches  of  zinc  surface  if  the  nickeling 
is  to  be  effected  in  the  above-named  space  of  time.  A  density 
of  current  of  1.4  to  1.5  amperes  and  4  to  4^  volts,  at  which  the 
sheets  have  to  remain  in  the  bath  for  3  minutes,  is  the  most 
suitable,  the  deposit  thus  obtained  being  in  every  respect  fault- 
less, provided  the  nickel  bath  is  of  proper  composition. 


208  ELECTRO-DEPOSITION   OF   METALS. 

For  nickeling  sheet  zinc  rolled  anodes  are,  as  a  rule,  only 
used,  except  when  working  with  baths  containing  boric  acid. 
The  anode  surface  must  at  least  be  equal  to  that  of  the  zinc 
surface  ;  the  distance  between  the  anodes  and  the  sheets  should 
be  from  3  to  3  ^  inches,  and  when  the  current-strength  is  some- 
what scant  the  distance  may  be  reduced  to  2^  inches.  The 
nickel  anodes  have  to  be  taken  from  the  bath  once  daily  and 
scoured  bright  with  scratch-brushes  and  sand ;  for  the  rest,  all 
the  rules  given  for  nickel  anodes  are  valid. 

Baths  used  for  nickeling  sheet  zinc  soon  become  alkaline  in 
consequence  of  the  powerful  current  used,  which  is  shown  by 
red  litmus-paper  turning  blue ;  the  alkalinity  also  manifests 
itself  by  the  bath  becoming  turbid  and  the  nickeling  not  turn- 
ing out  a  pure  white.  The  slightly  acid  reaction  is  restored  by 
citric  acid  solution.  The  appearance  of  the  dreaded  black 
streaks  and  stains  is  due  either  to  the  current  itself  being  too 
weak  or  to  its  having  been  weakened  by  an  extremely  great  re- 
sistance of  the  nickel  bath ;  also  to  an  insufficient  metallic  sur- 
face of  the  anodes,  which  may  be  either  too  small  or  not  suffi- 
ciently metallic  on  account  of  tarnishing;  and  finally  to  an 
excessive  alkalinity  of  the  bath  or  insufficient  contact  of  the 
hooks  with  the  connecting  rods. 

The  metallic  content  of  the  bath  must  from  time  to  time  be 
augmented  by  the  addition  of  nickel  salt,  and  the  bath  filtered 
at  certain  intervals.  When  the  conductivity  abates,  it  has  to  be 
restored  by  the  addition  of  conducting-salt. 

When  the  sheets  have  been  sufficiently  nickeled,  they  are 
allowed  to  drain  off,  then  plunged  into  hot  water,  and,  after  re- 
moving the  binding-screws,  dried  by  gentle  rubbing  with  fine 
sawdust  free  from  sand  and  passed  through  a  fine  sieve  to 
separate  pieces  of  wood.  In  all  manipulations,  the  unnickeled 
sides  are  placed  together,  while  a  piece  of  paper  of  the  size  and 
form  of  the  sheets  is  laid  between  the  nickeled  sides. 

The  nickeled  sheets  are  finally  polished,  which  is  effected  by 
placing  them  upon  supports  and  pressing  against  the  revolving 
bob  as  previously  described,  the  sheets  being,  however,  only 


DEPOSITION    OF    NICKEL   AND    COBALT.  2Og 

moderately  moistened  with  oil,  and  not  too  much  Vienna  lime 
applied  to  the  bob.  Polishing  is  done  first  in  one  direction  and 
then  in  another,  at  a  right  angle  to  this  first.  After  polishing, 
the  sheets  are  finally  cleansed  with  a  piece  of  soft  cloth  and 
impalpable  Vienna  lime,  after  which  they  should  show  a  pure 
white  lustrous  nickeling,  free  from  cracks  and  stains,  and  bear 
bending  and  rebending  several  times  without  the  nickeled  de- 
posit breaking  or  peeling  off. 

Nickeling  of  tin-plate.  For  elegant  and  durable  nickeling 
tin-plate  also  requires  previous  coppering.  The  deposit  is 
effected  with  a  less  powerful  current  than  for  sheet  zinc. 
Scouring  is  done  as  described  for  sheet  zinc,  also  polishing  of 
the  nickeled  tin-plate. 

Nickeling  copper  and  brass  sheets.  The  treatment  of  these 
sheets  differs  from  that  of  sheet  zinc  in  that  the  rough  sheets 
are  first  brushed  with  emery  and  then  polished  with  the  bob. 
After  treating  the  sheets  with  hot  caustic  lye  or  lime-paste, 
they  are  pickled  by  brushing  them  over  with  a  solution  of  I 
part  of  potassium  cyanide  in  20  parts  of  water.  They  are  then 
thoroughly  and  rapidly  rinsed  and  immediately  brought  into 
the  bath.  To  avoid  peeling  off,  the  current  must  not  be  too 
strong. 

Nickeling  of  sheet-iron  and  sheet-steel. — Only  the  best  qualtiy 
of  sheet  should  be  used  for  this  purpose.  After  rolling,  the 
sheets  are  freed  from  scales  by  pickling,  then  passed  through 
the  fine  rolls,  and  finally  again  pickled.  If  the  nickeled  sheets 
are  not  to  exhibit  a  high  degree  of  polish,  it  suffices  to  brush 
them  before  nickeling  with  a  large  broad  fibre  brush  (p.  136) 
and  emery  No.  oo.  But  for  a  high  lustre,  such  as  is  generally 
demanded,  the  sheets  have  first  to  be  ground.  For  fine  grind- 
ing the  pickled  sheets  broad  massive  cylinders  of  poplar  wood 
are  used,  which  are  covered  with  leather  and  turned  like  the 
disks  described  on  p.  132.  These  cylinders  are  10  to  12  inches 
in  diameter,  and  2  to  4  or  more  inches  long,  according  to  the 
size  of  the  sheets.  For  the  first  grinding,  the  cylinders  are 
coated  with  glue  and  rolled  in  emery  No.  100  to  120,  according 


210  ELECTRO-DEPOSITION   OF   METALS. 

to  the  condition  of  the  sheets,  while  emery  No.  oo  is  applied  to 
the  cylinders  used  for  the  fine  grinding.  The  grinding  is  suc- 
ceeded by  brushing,  as  described  on  p.  132. 

After  preparing  a  sufficiently  smooth  surface,  the  sheets  are 
at  once  rubbed  with  a  rag  moistened  with  petrolenm,  or,  if  pre- 
ferred, with  a  rag  and  pulverized  Vienna  lime ;  they  are  then 
scoured  wet  in  the  manner  described  for  sheet-zinc,  p.  204.  The 
scouring  material  must  be  liberally  applied,  especially  if  the 
sheets  are  to  be  directly  nickeled  without  previous  coppering, 
as  is  advisable.  After  rinsing  off  the  lime-paste,  the  sheets  are 
brushed  over  with  very  dilute  sulphuric  acid  (I  part  acid  to  25 
water),  rinsed  off,  then  lightly  brushed  over  once  more  with  lime- 
paste,  again  carefully  rinsed,  and  immediately  brought  into  the 
nickel  bath. 

The  current  should  be  neither  too  strong  nor  too  weak,  but 
regulated  so  that  the  nickeling  is  of  sufficient  thickness  in  15  to 
20  minutes  without  showing  a  tendency  to  peel  off.  It  is  not 
advisable  to  try  to  obtain  a  heavy  deposit  in  a  shorter  time,  be- 
cause it  would  lack  density,  which  is  the  principal  requirement 
for  nickeled  sheet-iron. 

After  nickeling,  the  sheets  are  rinsed  in  clean  water,  then 
plunged  into  hot  water  and  dried  by  rubbing  with  warm  saw- 
dust. After  this  operation,  it  is  recommended  to  thoroughly 
dry  the  sheets  in  an  oven  heated  to  between  176°  and  212°  F., 
to  expel  any  moisture  from  the  pores,  and  then  to  polish  them 
with  Vienna  lime  and  oil  or  with  rouge. 

Nickeling  of  wire. — Nickeling  of  wire  of  iron,  brass,  or  copper 
is  scarcely  ever  done  on  a  large  scale ;  it  is,  however,  believed 
that  the  nickeling  of  iron  and  steel  wires — for  instance,  piano- 
strings—might  be  of  advantage  to  prevent  rust  or  at  least  to  re- 
tard the  commencement  of  oxidation  as  long  as  possible. 

To  nickel  single  wires  cut  into  determined  lengths,  according 
to  the  general  rules  already  given,  is  simple  enough ;  but  this 
method  cannot  be  pursued  with  wire  several  hundred  yards  long, 
rolled  in  coils,  as  it  occurs  in  commerce.  Nickeling  the  wire  in 
coils,  however,  cannot  be  done,  as  only  the  upper  windings  ex- 


DEPOSITION   OF  NICKEL   AND    COBALT. 


211 


posed  to  the  anodes  would  acquire  a  coat  of  nickel.     Hence  it 
becomes  necessary  to  unwind  the  coil,  and  for  continuous  work- 


£    . 
£ 


y  M ' 


ti  i 


ing  pass  the  wire  at  a  slow  rate  through  the  cleansing  and  pick- 
ling baths,  as  well  as  the  nickel  bath  and  hot  water  reservoir,  as 


212  ELECTRO-DEPOSITION   OF   METALS. 

shown  in  Fig.  112  in  cross-section,  and  in  Fig.  113  in  ground 
plan. 

The  unwinding  of  the  wire  is  effected  by  a  slowly  revolving 
shaft,  upon  which  the  nickeled  wire  again  coils  itself ;  but  in  the 
illustration  the  shaft  is  omitted.  In  Fig.  1 13  four  wires  run  over 
the  four  rolls  a,  mounted  upon  a  common  shaft,  to  the  rolls  b 
upon  the  bottom  of  the  vat  A,  whereby  they  come  in  contact 
with  a  thickly  fluid  lime-paste  in  the  vat,  and  are  freed  from 
grease.  From  the  rolls  b  the  wires  run  through  the  wooden 
cheeks  i,  lined  with  felt,  which  retain  the  excess  of  lime-paste, 
and  allow  it  to  fall  back  into  the  vat.  The  wires  then  pass  over 
the  roll  c  to  the  roll  d.  Between  these  two  rolls  is  the  rose  g, 
which  throws  a  strong  jet  of  water  upon  the  wires,  thereby  free- 
ing them  from  adhering  lime-paste.  The  roll  dy  as  well  as  its 
axis,  is  of  brass,  and  to  the  latter  is  connected  the  negative  pole 
of  the  battery  or  dynamo,  so  that  by  carrying  the  wires  over  the 
roll  d  negative  electricity  is  conducted  to  them.  From  the 
roll  d  the  wires  run  over  the  roll-bench  s  (Fig.  113)  to  the  vat  C, 
which  contains  the  nickel  solution,  so  that  they  are  subjected  to 
the  action  of  the  anodes  arranged  in  this  vat  on  both  sides  of 
the  wires.  The  wires  then  pass  over  the  roll  e,  are  rinsed  under 
the  rose  h,  and  run  finally  through  a  hot  water  reservoir  and 
sawdust  (these  two  apparatuses  are  not  shown  in  the  illustra- 
tion), to  be  again  wound  in  coils.  In  case  a  high  polish  is  re- 
quired, the  nickeled  wires  may  be  run  under  pressure  through 
leather  cheeks  dusted  with  Vienna  lime. 

Nickeling  wire-gauze. — Messrs.  Louis  Lang  &  Son  obtained, 
in  1 88 1,  a  patent  for  a  method  of  nickeling  wire  gauze,  or  wire 
to  be  woven  into  gauze,  more  especially  for  the  purpose  of 
paper  manufacture.  These  wires,  which  are  generally  of  copper 
or  brass,  are  liable  to  be  attacked  by  the  small  quantities  of 
chlorine  which  generally  remain  in  the  paper  pulp,  by  which  the 
gauze  wire  eventually  suffers  injury.  To  nickel  wire  before  it 
is  woven,  it  is  wound  on  a  bobbin  and  immersed  in  a  nickel  bath 
in  which  it  is  coated  with  nickel  in  the  usual  way ;  it  is  then 
unwound  and  rewound  on  to  another  bobbin,  and  reimmersed 


DEPOSITION   OF  NICKEL   AND    COBALT.  213 

in  a  nickel  bath,  as  before,  so  as  to  coat  such  surfaces  as  were  in 
contact  with  each  other  and  with  the  first  bobbin.  To  deposit 
nickel  on  the  woven  tissues  it  may  either  be  coated  in  its  entire 
length,  as  it  leaves  the  loom,  or  in  detached  pieces.  For  this 
purpose  the  wire  gauze  is  first  immersed  in  a  pickle  bath,  and 
next  in  the  nickel  solution.  On  leaving  the  latter  it  is  rinsed 
and  then  placed  in  a  hot  air  chamber,  and  when  thoroughly  dry 
may  be  rolled  up  again  ready  for  use. 

Nickeling  of  knife-blades,  sharp  surgical  instruments,  etc. 

Considerable  trouble  is  frequently  experienced  in  nickeling 
sharp  edged  instruments,  the  edges  and  points  being  spoiled 
either  by  the  deposit  of  nickel  or  in  polishing.  And  yet  such 
instruments  can  be  readily  nickeled  in  such  a  manner  that  the 
edges  remain  in  as  good  condition  as  before. 

If  new  instruments  which  have  never  been  used  are  to  be 
nickeled,  no  special  preparation  is  required,  it  being  only 
necessary  to  free  them  at  once  from  grease  and  bring  them  into 
the  bath.  But  instruments  which  have  been  used  or  by  bad 
treatment  have  become  partly  or  entirely  covered  with  rust 
must  be  first  freed  from  rust  by  chemical  or  mechanical  treat- 
ment and  then  polished.  The  marks  left  by  the  stone  or  emery 
wheel  are  effaced  by  means  of  the  circular  brush,  this  treatment 
being  necessary  to  obtain  perfect  nickeling.  But  in  brushing 
the  edges  are  rendered  dull  if  special  precautionary  measures 
are  not  used.  For  instance,  the  edge  of  a  knife-blade  must 
never  come  in  contact  with  the  brush.  This  is  prevented  by 
firmly  pressing  the  blade  flat  upon  a  soft  support  of  felt  or 
cloth,  so  that  the  edge  sinks  somewhat  into  the  support,  with- 
out, however,  cutting  into  it.  The  edge  is  then  held  downward, 
and  thus  together  with  the  support  brought  against  the  revolv- 
ing brush.  In  this  manner  the  blades  may  be  vigorously 
brushed  without  fear  of  spoiling  the  edges. 

The  treatment  in  giving  them  a  high  polish  after  nickeling  is 
the  same.  Freeing  from  grease  may  be  done  in  the  usual 
manner  with  lime-paste ;  but  must  also  be  effected  upon  a  soft 


214  ELECTRO-DEPOSITION   OF   METALS. 

support,  the  same  as  in  polishing,  After  thorough  rinsing  in 
clean  water  the  separate  pieces,  without  being  previously  cop- 
pered, are  brought  directly  into  the  nickel  bath,  the  composi- 
tion of  which  must,  of  course,  be  suitable  for  nickeling  steel 
articles.  The  instruments  are  first  coated  with  the  use  of  a 
strong  current,  so  that  the  deposition  takes  place  slowly  and 
with  great  uniformity. 

In  suspending  the  articles  in  the  bath,  care  should  be  had 
that  neither  a  point  nor  an  edge  is  turned  towards  the  anodes. 
It  is  best  to  use  a  bath  with  anodes  on  one  side  only,  and  to 
suspend  the  blades  with  their  backs  towards  the  anodes.  If, 
for  any  reason,  the  instruments  are  to  be  suspended  between 
two  rows  of  anodes,  the  edges  should  be  uppermost,  as  near  as 
possible,  to  the  level  of  the  bath ;  but  they  should  never  hang 
deep  or  downwards. 

After  nickeling  the  instruments  are  polished  for  high  lustre, 
but  must  always  be  exposed  upon  a  soft  support,  as  above  de- 
scribed, to  the  action  of  a  felt  disk,  or,  still  better,  of  a  cloth 
bob. 

Nickeling  of  electrotypes,  cliches,  etc. — The  advantages  of 
nickeling  electrotypes,  etc.,  over  steeling  will  be  discussed  under 
"  Steeling,"  and  hence  only  the  most  suitable  composition  of 
the  nickel  baths  and  the  manipulations  required  will  here  be 
given. 

The  nickel  baths  according  to  formula  III.  (page  174)  and 
formula  VII.  (page  177)  are  the  most  suitable  for  simple  nickel- 
ing, because  the  ammonium  sulphate  not  being  present  in  too 
great  an  excess,  as  well  as  the  presence  of  boric  acid,  causes 
the  nickel  to  separate  with  great  hardness.  With  nickeled 
electro-plates  three  times  as  large  an  edition  can  be  printed  as 
with  plates  of  the  same  material  not  nickeled. 

It  being  a  well-known  fact  that  a  fused  alloy  of  nickel  with 
cobalt  possesses  greater  hardness  than  either  of  the  metals  by 
themselves,  experiments  proved  that  an  electro-deposited 
nickel-cobalt  alloy  exhibited  the  same  behavior,  the  greatest 
degree  of  hardness  being  attained  with  an  addition  of  cobalt 


DEPOSITION   OF   NICKEL   AND    COBALT. 

varying  between  25  and  30  per  cent.  For  this  deposit  the  term 
hard  nickeling  is  proposed,  the  most  suitable  baths  for  the  pur- 
pose being  prepared  according  to  the  following  formulae :  1. 
Nickel-ammonium  sulphate  21.16  ounces,  cobalt-ammonium 
sulphate  5.29  ounces,  ammonium  sulphate  8.8  ounces,  water 
15  quarts;  or,  II.  Nickel-ammonium  sulphate  21. 16  ounces, 
cobalt-ammonium  sulphate  5.29  ounces,  crystallized  boric  acid 
10.58  ounces,  water  15  quarts. 

Bath  No.  I.  is  prepared  by  simply  dissolving  the  salts  in 
heated  water,  and,  in  case  the  bath  is  too  acid,  adding  spirits 
of  sal  ammoniac  until  blue  litmus-paper  is  only  slightly  red- 
dened. It  is  best  to  use  rolled  and  cast  anodes  in  equal  pro- 
portions ;  and  when  the  bath  becomes  alkaline  to  restore  its 
original  slightly  acid  reaction  by  the  addition  of  citric  acid. 

To  prepare  bath  No.  II.  dissolve  the  constituents  by  boiling; 
and  in  case  not  entirely  neutral  metallic  salts  have  been  used, 
add  to  the  hot  solution,  with  constant  stirring,  I  to  I  ^  ounces 
of  nickel  carbonate  for  the  neutralization  of  free  sulphuric  acid 
which  may  be  present.  This  bath  must  not  be  neutralized,  but 
worked  with  its  strongly  acid  reaction,  mixed  anodes  being  also 
used. 

The  bath  prepared  according  to  formula  No.  II.  deserves  the 
preference,  it  yielding  a  harder  deposit  than  bath  No.  I. 

For  the  rest,  the  treatment  of  the  baths  is  the  same  as  that 
given  for  nickel  baths  of  similar  composition  (pp.  174  and  177), 
and  the  process  of  h:rd  nickeling  does  not  essentially  differ 
from  ordinary  nickeling.  The  suspending  hooks  are  soldered 
to  the  backs  of  the  plates  by  means  of  the  soldering-iron  and  a 
drop  of  tin ;  or  the  plates  are  secured  in  holders  of  sheet-cop- 
per o.i  i  inch  thick,  and  ^  to  I  inch  wide,  of  the  form  shown 
in  Fig.  114.  The  printing  surface  is  freed  from  grease  by 
brushing  with  lime-paste,  rinsed  in  water,  and  then  brushed 
with  a  clean  brush  to  remove  the  lime  from  the  depressions. 
The  plates  are  then  hung  in  the  bath  and  covered  with  a  strong 
current.  When  everywhere  coated  with  nickel  the  current  is 
weakened  and  the  deposit  allowed  gradually  to  augment. 


216 


ELECTRO-DEPOSITION    OF    METALS. 


With  an  average  duration  of  nickeling  of  15  to  20  minutes, 
with  2.8  to  3  volts,  the  deposit  will,  as  a  rule,  be  sufficiently 
resisting. 

The  nickeled  plates  are  rinsed  in  water,  then  plunged  in  hot 
water,  and  dried  in  sawdust,  when  the  nickeled  printing  surface 
may  be  brushed  over  with  a  brush  and  fine  whiting,  it  being 

FIG.  114. 


claimed  that  plates  thus  treated  take  printing-ink  better,  while 
the  first  impressions  of  plates  not  brushed  with  whiting  are 
somewhat  dull. 

Nickel-facing  is  especially  suitable  for  copper  plates  for  color- 
printing,  the  nickel  not  being  attacked  like  copper  or  iron  by 
vermilion. 

Recovery  of  nickel  from  old  baths. — At  the  present  low  price 
of  nickel  its  recovery  from  old  solutions  scarcely  pays.  The 
uselessness  of  the  bath  is  in  most  cases  due  to  two  causes  :  it  has 
either  become  too  poor  in  metal  or  it  contains  foreign  metallic 
admixtures.  In  the  first  case,  the  expense  of  evaporating  with 
the  further  manipulation  is  out  of  proportion  to  the  value  of  the 


DEPOSITION   OF   NICKEL   AND    COBALT.  2I/ 

nickel  recovered ;  and,  in  the  second  case,  the  reduction  of  the 
foreign  metals  is  inconvenient  and  connected  with  expenses 
making  it  unprofitable. 

Urquhart  proposes  the  following  plan  for  recovering  nickel 
from  old  solutions ;  Make  a  saturated  solution  of  ammonium 
sulphate  in  warm  water,  and  add  to  it  the  old  nickel-plating 
solution  with  constant  stirring,  and,  after  the  lapse  of  a  few 
minutes,  a  granular  precipitate  of  the  double  sulphate  of  nickel 
and  ammonium  will  begin  to  separate.  The  addition  of  am- 
monium sulphate  should  be  continued  from  time  to  time  until 
the  liquid  is  colorless.  The  precipitated  salt  is  very  pure,  and 
may  be  used  directly  in  making  a  new  bath. 

To  improve  defective  nickeling. — With  the  basis-metal  thor- 
oughly cleansed  defective  places  should  not  occur,  but  when 
they  happen,  by  accident  or  negligence,  recourse  is  to  had  to 
"doctoring."  The  "  doctor"  is  arranged  as  follows :  A  piece 
of  stout  copper  wire  is  bent  in  the  form  of  a  hook  at  each  end, 
and  a  fragment  of  nickel  anode  is  fastened  firmly  to  one  of  the 
hooks  with  a  piece  of  twine.  The  fragment  of  anode  is  then 
wrapped  in  several  folds  of  muslin,  the  second  hook  connected 
by  a  wire  to  the  anode-rod  of  the  bath,  and  the  article  put  in 
contact  with  the  negative  electrode.  The  rag  end  is  now  dipped 
in  the  nickel  bath,  applied  to  the  defective  spot,  and  allowed  to 
rest  upon  it  for  a  few  moments,  then  dipped  again  and  reap- 
plied.  By  repeatedly  dipping  the  rag  in  the  nickel  bath  and 
applying  it  in  this  way  a  sufficient  coating  of  nickel  may  be 
given  in  a  few  minutes ;  and  if  the  operation  is  skillfully  per- 
formed, no  trace  of  the  patch  will  be  observable  after  polishing. 

Nickeling  by  contact  and  boiling. — Franz  Stolba  has  described 
a  nickeling  process  by  contact,  which  is  executed  as  follows : — 

In  a  bright  copper  kettle  heat  to  boiling  a  concentrated  solu- 
tion of  zinc  chloride  with  an  equal  or  double  the  volume  of  soft 
water,  and  then  add  drop  by  drop  pure  hydrochloric  acid  until 
the  precipitate  formed  by  diluting  the  zinc  chloride  solution 
with  water  disappears.  Then  add  as  much  zinc  powder  as  will 
lie  upon  the  point  of  a  knife,  the  effect  of  this  addition  being 


2l8  ELECTRO-DEPOSITION    OF   METALS. 

that  the  copper  of  the  kettle  as  far  as  it  comes  in  contact  with 
the  solution  is  in  a  few  minutes  zincked.  Now  bring  into  the 
kettle  sufficient  nickel  salt,  best  nickel  sulphate,  to  color  the 
fluid  perceptibly  green ;  then  introduce  the  articles  to  be  nick- 
eled together  with  small  pieces  .of  sheet  zinc  or  zinc  wire,  so  as 
to  present  many  points  of  contact,  and  continue  boiling.  With 
a  correct  execution  of  the  process  it  is  claimed  the  articles  will 
be  uniformly  nickeled  in  15  minutes;  if  such  is  not  the  case, 
the  boiling  must  be  continued,  fresh  pieces  of  zinc  added,  or,  if 
the  solution  does  not  appear  sufficiently  green,  fresh  nickel  salt 
introduced. 

For  the  success  of  the  process  "several  conditions  are  neces- 
sary. The  metallic  articles  must  be  thoroughly  free  from 
grease,  as  otherwise  no  deposit  of  nicfcel  is  formed  on  the  greasy 
places.  In  boiling,  the  solution  must  not  become  turbid  by  the 
separation  of  basic  zinc  salt,  nor  acid  by  free  hydrochloric  acid, 
otherwise  the  nickeling  will  be  duJl  and  blackish.  Hence,  any 
turbidity  must  be  at  once  removed  by  adding  drop  by  drop 
hydrochloric  acid,  and  too  great  acidity  by  the  careful  addition 
of  solution  of  carbonate  of  soda.  The  articles  thus  nickeled 
are  to  be  thoroughly  washed  with  water,  dried,  and  polished 
with  whiting. 

Since  stains  are  readily  formed  by  this  process,  especially 
when  nickeling  polished  iron  and  steel  articles,  on  the  places 
where  the  metal  to  be  nickeled  comes  in  contact  with  the  zinc, 
Stolba  in  later  experiments  omitted  the  zinc,  and  thus  the  con- 
tact process  becomes  a  boiling  process.  To  a  10  per  cent, 
solution  of  zinc  chloride  add  enough  nickel  sulphate  to  give  the 
solution  a  deep  green  color  and  then  heat,  best  in  a  porcelain 
vessel,  to  the  boiling-point.  Then  without  troubling  about  the 
turbidity  of  the  bath  caused  by  the  separation  of  a  basic  zinc 
salt,  immerse  the  objects,  previously  cleansed  and  freed  from 
grease,  in  it  in  such  a  way  that  they  do  not  touch  each  other, 
or  at  least  in  only  a  few  places,  and  keep  the  whole  boiling  30 
to  60  minutes,  from  time  to  time  replacing  the  water  lost  by 
evaporation.  The  after-treatment  is  the  same  as  given  above 


DEPOSITION   OF  NICKEL  AND    COBALT.  2IQ 

for  the  contact  process  ;  the  deposit  of  nickel  is,  of  course,  very 
thin. 

This  process,  while  suitable  for  the  amateur,  cannot  be  rec- 
ommended to  the  professional  electro-plater,  the  results  not 
being  sufficiently  sure.  A  thin  deposit  of  nickel  of  a  light  color 
may  be  obtained  upon  brass  articles,  but  that  upon  iron  articles 
is  dark  and  mostly  stained. 

Small  articles,  which  are  not  to  be  nickeled  by  the  battery, 
are  preferably  coated  by  contact  with  cobalt  by  the  process  to 
be  described  later  on,  under  "  Electro-cobalting."  The  higher 
price  of  cobalt  salts  makes  little  difference,  small  quantities  only 
being  required,  and  the  color  of  cobalt  can  scarcely  be  distin- 
guished from  that  of  nickel. 

By  boiling  a  solution  of  8j^  ozs.  of  nickel-ammonium  sulphate 
and  Sj/2  ozs.  of  ammonium  chloride  in  I  quart  of  water*,  together 
with  clean  iron  filings  free  from  grease,  and  introducing  into 
the  fluid  copper  or  brass  articles,  the  latter  become  coated  with 
a  thin  layer  of  nickel  capable  of  bearing  light  polishing.  The 
nickel  solution  has  to  be  frequently  renewed. 

According  to  R.  Kaiser,  an  alloy  containing  nickel  may  be 
deposited  upon  articles  by  proceeding  as  follows :  Melt  I  part 
of  copper  and  5  of  tin,  and  granulate  the  fused  mass  by  pouring 
it  through  a  heated  sheet-iron  sieve  into  a  bucket  filled  with 
water.  Boil  the  granulated  metal  thus  obtained  with  tartar  free 
from  lime,  and  add  for  every  100  parts  by  weight  of  granulated 
metal  0.5  part  of  glowed  nickel  oxide.  Then  bring  the  brass  or 
copper  articles,  previously  freed  from  grease  and  pickled,  into 
the  boiling  fluid,  and  after  boiling  for  a  short  time  they  will  ap- 
pear coated  with  a  white  alloy  resembling  German  silver.  The 
addition  of  nickel  oxide  must  be  repeated  from  time  to  time. 
Iron  and  steel  articles  are  to  be  previously  coppered.  By  add- 
ing nickel  carbonate  to  this  bath,  it  is  claimed,  coats  richer  in 
nickel  and  of  a  darker  color  than  that  of  platinum  to  blue-black 
are  obtained. 

Deposits  of  nickel  alloys. — From  suitable  solutions  of  the 
metallic  salts  nickel  may  be  deposited  together  with  copper  and 


220  ELECTRO- DEPOSITION   OF   METALS. 

tin,  as  well  as  with  copper  and  zinc.  With  the  first  combina- 
tion, especially,  all  tones  from  copper-red  to  gold-shade  may  be 
obtained,  according  to  which  metal  predominates,  or  according 
to  the  current-strength  which  is  conducted  into  the  bath,  as  is 
also  the  case  in  brassing. 

A  suitable  bath  for  coating  metallic  articles  with  an  alloy  of 
nickel,  copper,  and  tin,  for  which  the  term  nickel- bronze  is  pro- 
posed, is  obtained  by  dissolving  the  metallic  phosphates  in 
sodium  pyrophosphate  solution.  By  mixing  solution  of  blue 
vitriol  with  solution  of  sodium  phosphate,  cupric  phosphate  is 
precipitated  which  is  filtered  off  and  washed.  In  the  same 
manner  nickel  phosphate  is  prepared  from  a  solution  of  nickel- 
sulphate.  These  phosphates  are  then,  each  by  itself,  dissolved 
in  a  concentrated  solution  of  sodium  pyrophosphate,  while 
chloride  of  tin  is  directly  dissolved  in  sodium  pyrophosphate 
until  the  turbidity,  at  first  rapidly  disappearing,  disappears  but 
slowly. 

Nothing  definite  can  be  said  in  regard  to  the  mixing  propor- 
tions of  these  three  solutions,  because  the  proportions  will  have 
to  be  varied  according  to  the  desired  color  of  the  deposit ;  the 
operator,  however,  will  soon  find  out  of  which  solution  more 
must  be  added  in  order  to  obtain  the  tone  desired. 

For  depositing  an  alloy  of  nickel,  copper,  and  zinc,  solutions 
of  cupric  sulphate  (blue  vitriol)  and  zinc  white  in  potassium 
cyanide,  to  which  is  added  an  ammoniacal  solution  of  nickel 
carbonate,  may  be  advantageously  used. 

According  to  a  French  process,  a  deposit  of  German  silver 
may  be  obtained  as  follows  :  Dissolve  a  good  quality  of  German 
silver  in  nitric  acid  and  add,  with  constant  stirring,  solution  of 
potassium  cyanide  until  all  the  metal  is  precipitated  as  cyanide. 
The  precipitate  is  then  filtered  off,  washed,  dissolved  in  potassium 
cyanide,  and  the  solution  diluted  with  double  the  volume  of 
water.  This  process,  however,  does  not  seem  very  feasible, 
since  nickel  separates  with  difficulty  from  its  cyanide  combi- 
nation. 

Watt  recommends  the  following  method :   Cut  up  into  small 


DEPOSITION   OF   NICKEL   AND    COBALT.  221 

pieces  sheet  German  silver  about  I  oz.,  place  the  strips  in  a 
glass  flask,  and  add  nitric  acid  diluted  with  an  equal  bulk  of 
water.  Assist  the  solution  of  the  metal  by  gentle  heat.  When 
red  fumes  cease  to  appear  in  the  bulb  of  the  flask,  decant  the 
liquor  and  apply  fresh  acid,  diluted  as  before,  to  the  undissolved 
metal,  taking  care  to  avoid  excess ;  it  is  best  to  leave  a  small 
quantity  of  undissolved  metal  in  the  flask,  by  which  an  excess 
of  acid  is  readily  avoided.  The  several  portions  of  the  metallic 
solutions  are  to  be  mixed  and  diluted  with  about  3  pints  of  cold 
water  in  a  gallon  vessel.  Next  dissolve  about  4  ozs.  of  car- 
bonate of  potash  in  a  pint  of  water,  and  add  this  gradually  to 
the  former,  with  gentle  stirring,  until  no  further  precipitation 
takes  place.  The  precipitate  must  be  washed  several  times 
with  hot  water,  and  then  redissolved  by  adding  a  strong  solu- 
tion of  cyanide,  with  stirring,  and  about  I  oz.  of  liquid  am- 
monia. To  avoid  adding  too  great  an  excess  of  cyanide,  it  is  a 
good  plan,  when  the  precipitate  is  nearly  all  dissolved,  to  let  it 
rest  for  half  an  hour  or  so,  then  decant  the  clear  liquor,  and 
dissolve  the  remainder  of  the  precipitate  separately.  A  small 
excess  of  cyanide  solution  may  be  added  as  "  free  cyanide," 
and  the  whole  mixed  together  and  made  up  to  one  gallon  with 
cold  water.  The  solution  should  then  be  filtered  or  allowed  to 
repose  for  about  12  hours,  and  the  clear  liquor  then  carefully 
decanted  from  any  sediment  which  may  be  present  from  cyanide 
impurities.  The  bath  must  be  worked  with  a  German-silver 
anode,  which  should  be  of  the  same  quality  as  that  from  which 
the  solution  is  prepared  ;  a  Bunsen  battery  should  be  employed 
as  the  source  of  electricity,  or  a  dynamo-machine. 

2.   Cobalting. 

Properties  of  cobalt. — Cobalt  has  nearly  the  same  color  as 
nickel,  with  a  slightly  reddish  tinge ;  its  specific  gravity  is  8.56. 
It  is<  exceedingly  hard,  highly  malleable  and  ductile,  and  capa- 
ble of  taking  a  polish.  It  is  slightly  magnetic,  and  preserves 
this  property  even  when  alloyed  with  mercury.  It  is  rapidly 
dissolved  by  nitric  acid,  and  slowly  by  dilute  sulphuric  and 
hydrochloric  acids. 


222  ELECTRO-DEPOSITION   OF   METALS. 

For  cobalting,  the  baths  given  under  nickeling  may  be  used 
by  substituting  for  the  nickel  salt  a  corresponding  quantity  of 
cobalt  salt.  By  observing  the  rules  given  for  nickeling,  the 
operation  proceeds  with  ease.  Anodes  of  metallic  cobalt  are  to 
be  used  in  place  of  nickel  anodes. 

Nickel  being  cheaper  and  its  color  somewhat  whiter,  electro- 
plating with  cobalt  is  but  little  practised.  On  account  of  the 
greater  solubility  of  cobalt  in  dilute  sulphuric  acid  it  is,  however, 
under  all  circumstances,  to  be  preferred  for  facing  valuable  cop- 
per plates  for  printing. 

According  to  the  more  or  less  careful  adjustment  of  such 
plates  in  the  press,  many  places  of  the  facing  are  more  or  less 
attacked,  and  it  may  be  desired  to  remove  the  coating  and  make 
a  fresh  deposit.  For  this  purpose,  Gaifife  has  proposed  the  use 
of  cobalt  in  place  of  nickel,  because  the  former  dissolves  slowly 
but  completely  in  dilute  sulphuric  acid.  He  recommends  a 
solution  of  i  part  of  chloride  of  cobalt  in  10  of  water.  The  so- 
lution is  to  be  neutralized  with  aqua  ammonia,  and  the  plates 
are  to  be  electro-plated  with  the  use  of  a  moderate  current. 

Cobalt  precipitated  from  its  chloride  solution  does  not  how- 
ever yield  a  hard  coating,  and  hence  the  following  bath  is  recom- 
mended for  the  purpose :  Double  sulphate  of  cobalt  and  am- 
monium 21  ozs.,  cobaltous  carbonate  0.8  oz..  crystallized  boric 
acid  10^  ozs.,  water  10  quarts. 

The  bath  is  prepared  in  the  same  manner  as  No.  VII.,  given 
under  "Nickeling."  It  requires  a  tension  of  2.5  to  2.75  volts. 

To  determine  whether  and  how  much  copper  is  dissolved  in 
stripping  the  cobalt  deposit  from  cobalted  copper  plates,  a  cop- 
per plate  with  a  surface  of  7^  square  inches  was  coated  with 
7.71  grains  of  cobalt  and  placed  in  dilute  sulphuric  acid  (i  part 
acid  of  66°  Be.,  to  12.5  parts  of  water).  After  the  acid  had  acted 
for  1 6  hours,  the  cobalt  deposit  was  partially  dissolved  and  had 
partially  collected  in  lamina  upon  the  bottom  of  the  vessel,  the 
copper  plate  being  entirely  freed.  On  weighing  the  copper  plate 
it  was  shown  that  it  had  lost  about  0.0063  Per  cent.,  this  loss 
being  apparently  chiefly  from  the  back  of  the  plate,  the  engraved 


DEPOSITION    OF   NICKEL   AND    COBALT.  223 

side  exhibiting  no  trace  of  corrosion.  This  experiment  proved 
that  there  is  no  danger  of  destroying  the  copper  plate  by  strip- 
ping the  cobalt  deposit  with  dilute  sulphuric  acid,  provided  the 
operation  is  executed  with  due  care  and  attention. 

Warren  has  described  a  cobalt  solution  which  can  be  de- 
composed in  a  single  cell  apparatus,  and  for  this  reason  would 
seem  suitable  for  electro-plating  small  articles  en  masse.  For 
the  preparation  of  this  bath  dissolve  3J^  ounces  of  chloride  of 
cobalt  in  as  little  water  as  possible,  and  compound  the  solution 
with  concentrated  solution  of  Rochelle  salt  until  the  voluminous 
precipitate  at  first  formed  is  almost  entirely  redissolved,  and 
then  filter.  Bring  the  bath  into  a  vessel  and  place  the  latter  in 
a  clay  cell  filled  with  concentrated  solution  of  sal  ammoniac  or 
of  common  salt  and  containing  a  zinc  cylinder.  Connect  the 
objects  to  be  plated  to  the  zinc  by  a  copper  wire  and  allow 
them  to  dip  in  the  cobalt  solution.  With  a  closed  current  the 
objects  become  gradually  coated  with  a  lustrous  cobalt  deposit 
which,  after  2  hours,  is  sufficiently  heavy  to  bear  vigorous 
polishing  with  the  bob.  Zinc  may  be  coated  in  the  same 
manner. 

The  following  solution  has  been  recommended  by  Mr.  G.  W. 
Beardslee,  of  Brooklyn,  N.  Y.,  and  is  claimed  to  yield  a  good 
deposit  of  cobalt  which  is  very  white,  exceedingly  hard,  and 
tenaciously  adherent:  Dissolve  pure  cobalt  in  boiling  hydro- 
choloric  acid  and  evaporate  the  solution  to  dryness.  Next  dis- 
solve 4  to  6  ozs.  of  the  resulting  salt  in  I  gallon  of  distilled 
water,  to  which  add  liquid  ammonia  until  it  turns  red  litmus- 
paper  blue.  The  solution  being  thus  rendered  slightly  alka- 
line, is  ready  for  use.  A  battery  power  of  from  two  to  five 
Smee  cells  will  be  sufficient  to  do  good  work.  Care  must  be 
had  not  to  allow  the  solution  to  lose  its  slightly  alkaline  con- 
dition, upon  which  the  whiteness,  uniformity  of  deposit,  and  its 
adhesion  to  the  basis-metal  greatly  depend. 

For  cobalting  small  fancy  articles  of  copper,  brass,  or  steel, 
R.  Daub  recommends  the  following  bath:  Dissolve  4^  ozs.  of 
double  sulphate  of  cobalt  and  ammonium  in  4^  quarts  of 


224  ELECTRO-DEPOSITION    OF   METALS. 

water.  The  solution  should  show,  at  59°  F.,  a  specific  gravity 
of  1.015.  The  most  suitable  current-strength  is  0.8  ampere 
with  about  two  volts.  The  size  of  the  anodes  is  of  great  influ- 
ence as  regards  the  uniformity  of  the  cobalting.  For  the 
deposition  of  cobalt  upen  brass,  copper,  steel,  or  iron,  the 
anodes  may  consist  of  rolled  cobalt  in  strips  about  2  inches 
wide  and  10  to  12  inches  long,  according  to  the  size  of  the  arti- 
cles. The  anodes  are  arranged  on  the  sides  of  the  vat,  about  6 
inches  apart.  With  the  use  of  a  large  vat — holding  from  500 
to  1000  quarts  of  bath — a  corresponding  series  of  such  anodes 
are  to  be  suspended  to  a  conducting  rod  which  rests  length- 
wise upon  the  ends  of  the  vat.  The  metallic  articles  should  be 
coated  with  a  thin  film  of  cobalt  in  a  few  seconds  after  having 
been  suspended  in  the  bath,  and  the  current  strength  is  then 
reduced,  to  be  increased  only  when  more  articles  are  brought 
into  the  bath.  The  mode  of  treatment  is  different  from  that  in 
the  nickel  bath,  and,  since  cobalt  deposits  with  greater  ease 
than  nickel,  the  regulation  of  the  current  is  the  principal  point. 
The  current-strength  should  be  reduced  as  soon  as  the  articles 
are  entirely  and  nicely  coated  with  cobalt.  Copper  articles  re- 
quire at  the  beginning  a  stronger  current  than  brass  objects, 
while  for  articles  of  iron  or  steel  the  current  should  be  weaker 
than  for  either  brass  or  copper.  Places  in  relief  should  be  kept 
as  far  as  possible  from  the  anodes  to  prevent  blackening  or 
burning.  According  to  R.  Daub,  the  principal  condition  for 
the  success  of  the  operation  is  to  maintain  a  uniform  density  of 
the  bath,  either  by  the  addition  of  water  or  of  cobalt  salt,  as 
may  be  required.  The  color  of  the  deposit  is  much  influenced 
by  the  current-strength.  Thus  a  deposit  with  I  volt  and  a  large 
anode-surface  is  not  so  white  as  one  with  two  volts  and  a 
smaller  anode-surface,  about  2/$  of  that  of  the  cathode.  Cast- 
brass  is  especially  suitable  for  cobalting,  as  well  as  metallic 
articles  which  are  kept  in  dry  rooms  or  used  for  ornamental 
purposes. 

Cobalting  by  contact. — While  nickeling  by  contact  with  zinc 
yields  only  incomplete  results,  the  cobalting  of  copper  and  brass 


DEPOSITION   OF   COPPER,  BRASS,  AND   BRONZE.  225 

articles  succeeds  very  well  with  the  use  of  the  following  bath : 
Crystallized  cobalt  sulphate  0.35  oz.,  crystallized  sal  ammoniac 
0.07  oz.,  water  I  quart.  Heat  the  bath  to  between  104°  and  122° 
F.,  and  immerse  the  previously  cleansed  and  pickled  articles  in 
the  bath,  bringing  them  in  contact  with  a  bright  zinc  surface  not 
too  small ;  for  small  articles  a  zinc  sieve  may  be  used.  In  3  or 
4  minutes  the  coating  is  heavy  enough  to  bear  vigorous  polishing. 


CHAPTER  VIII. 

DEPOSITION   OF   COPPER,  BRASS,  AND  BRONZE. 

i.  COPPERING. 

Properties  of  copper. — Copper  has  a  characteristic  red  color, 
and  possesses  strong  lustre ;  it  is  very  tenacious,  may  be  rolled 
to  thin  lamina,  and  readily  drawn  into  fine  wire.  The  specific 
gravity  of  wrought  copper  is  8.95,  and  of  cast  8.92.  Copper 
fuses  more  readily  than  gold,  but  with  greater  difficulty  than 
silver. 

In  a  humid  atmosphere  containing  carbonic  acid,  copper  be- 
comes gradually  coated  with  a  green  deposit  of  basic  carbonate ; 
when  slightly  heated  it  acquires  a  red  coating  of  cuprous  oxide, 
and  when  strongly  heated  a  black  coating  of  cupric  oxide  with 
some  cuprous  oxide.  Copper  is  most  readily  attacked  by  nitric 
acid,  but  is  slowly  dissolved  when  immersed  in  heated  hydro- 
chloric or  sulphuric  acid ;  with  exclusion  of  the  air,  it  is  not 
dissolved  by  dilute  sulphuric  or  hydrochloric  acid,  and  but 
slightly  with  admission  of  the  air.  Liquid  ammonia  causes  a 
rapid  oxidation  of  copper  in  the  air  and  the  formation  of  a  blue 
solution.  An  excess  of  potassium  cyanide  dissolves  copper. 
Sulphuretted  hydrogen  blackens  bright  copper. 

Copper  baths. — The  composition  of  these  baths  depends  on 
the  purpose  they  are  to  serve,  and  below  are  mentioned  the 
most  approved  baths,  with  the  exception  of  the  acid  copper 
15 


226  ELECTRO-DEPOSITION    OF   METALS. 

bath  used  for  plastic  deposits  of  copper,  which  will  be  discussed 
later  on  under  "  Copper  galvanoplasty." 

In  most  cases  the  more  electro-positive  metals,  zinc,  iron,  tin, 
etc.,  are  to  be  coppered  either  as  preparation  for  the  succeed- 
ing process  of  nickeling,  silvering,  or  gilding,  or  to  protect 
them  against  oxidation,  or  for  the  purpose  of  decoration.  The 
above-mentioned  electro-positive  metals,  however,  decompose 
acid  copper  solutions  and  separate  from  them  pulverulent  cop- 
per, while  an  equivalent  portion  of  zinc,  iron,  tin,  etc.,  is  dis- 
solved. For  this  reason,  such  solutions  of  copper  cannot  be 
used  for  coating  these  metals  for  this  purpose,  alkaline  copper 
baths  being  exclusively  employed,  which  may  be  arranged 
under  two  groups — those  containing  potassium  cyanide,  and 
those  without  it. 

Hassauer  prepares  a  copper  bath  by  dissolving  3*^  ozs.  of 
copper  cyanide  in  a  solution  of  i/j^  ozs.  of  70  per  cent, 
potassium  cyanide  in  3  quarts  of  water,  boiling,  filtering,  and 
diluting  with  7  quarts  of  water  to  a  lo-quart  bath.  This  bath 
works  very  well  when  heated  to  between  113°  and  122°  F., 
but  when  used  cold  requires  a  very  strong  current,  and  hence 
the  use  of  the  following  formulae  is  recommended: — 

Copper  baths  for  iron  and  steel  articles. — I .  To  be  used  at  the 
ordinary  temperature. — Water  10  quarts,  bisulphite  of  soda  in 
powder  7  ozs.,  crystallized  carbonate  of  soda  14  ozs.,  neutral 
acetate  of  copper  7  ozs.,  75  per  cent,  potassium  cyanide  7  ozs., 
spirits  of  sal  ammoniac  4.4  ozs. 

1 1 ,  For  hot  coppering  (  at  between  140°  and  158°  F. )  Rose  leu  r 
recommends:  Water  10  quarts,  bisulphite  of  soda  in  powder 
2 1  ozs.,  crystallized  carbonate  of  soda  7  ozs.,  neutral  acetate  of 
copper  7  ozs.,  75  per  cent,  cyanide  of  potassium  9|  ozs.,  spirit 
of  sal  ammoniac  4  ozs. 

The  baths  are  best  prepared  as  follows :  Dissolve  the  bisul- 
phite and  carbonate  of  soda  in  one-half  the  water,  the  potassium 
cyanide  in  the  other  half,  and  mix  the  copper  salt  with  the 
spirit  of  sal  ammoniac ;  then  pour  the  blue  ammoniacal  copper 
solution  into  the  solution  of  the  soda  salts,  and  finally  add  the 


DEPOSITION   OF   COPPER,  BRASS,  AND   BRONZE.  227 

potassium  cyanide  solution;  the  bath  will  then  be  clear  and 
colorless.  Boiling,  though  not  absolutely  necessary,  is  of  ad- 
vantage, after  which  the  solution  is  to  be  filtered. 

According  to  full  investigations  made,  the  excess  of  carbonate 
of  soda  in  formula  I.  serves  no  special  purpose,  but  on  the 
contrary,  in  many  cases,  is  directly  detrimental ;  neither  is  the 
use  of  ammonia  of  any  special  advantage,  and  it  may  just  as 
well,  or  rather  better,  be  omitted.  Further,  the  use  of  separate 
baths  for  cold  and  warm  coppering  is  at  least  questionable.  It 
is  believed  that  a  single  bath  suffices  for  both  cases,  heating 
having  been  found  of  special  advantage  only  for  rapid  and 
thick  coppering,  or  for  obtaining  particular  shades  which  are 
produced  with  difficulty  in  the  cold  bath,  but  without  trouble  in 
the  heated  bath. 

The  following  formula  may  be  highly  recommended,  a  cop- 
per bath  composed  according  to  it  always  yielding  good  and 
sure  results : — 

III.  Water  10  quarts,  crystallized  carbonate  of  soda  8^  ozs., 
crystallized  bisulphite  of  soda  7  ozs.,  neutral  acetate  of  copper 
7  ozs.,  98  or  99  per  cent,  potassium  cyanide  8^  ozs. 

The  bath  is  prepared  as  follows :  Dissolve  in  7  quarts  of 
warm  water  the  carbonate  of  soda,  gradually  add  the  bisulphite 
of  soda  to  prevent  violent  effervescence,  and  then  add,  with 
vigorous  stirring,  the  acetate  of  copper  in  small  portions. 
Dissolve  the  potassium  cyanide  in  3  quarts  of  cold  water,  and 
mix  both  solutions  when  the  first  is  cold.  By  thorough  stirring 
with  a  clean  wooden  stick  a  clear  solution  is  quickly  obtained 
which  is  allowed  to  settle  and  siphoned  off  clear.  If  after  the 
addition  of  the  potassium  cyanide  the  bath  should  not  become 
colorless,  or  at  least  wine-yellow,  add  a  small  quantity  more  of 
potassium  cyanide.  This  bath  does  not  require  a  strong  cur- 
rent, and  yields  an  especially  heavy  coppering  of  a  beautiful 
red  color;  a  current  of  0.4  ampere  at  a  tension  of  3  to  3.5  volts 
is  calculated  for  15^  square  inches  of  surface  of  objects. 
With  a  greater  content  of  potassium  cyanide  the  tension  may 
be  correspondingly  decreased. 


228  ELECTRO-DEPOSITION   OF   METALS. 

For  coppering  zinc  articles,  Roseleur  recommends  the  follow- 
ing bath : — 

IV.  Water  10  quarts,  tartar,  free  from  lime,  6.7  ozs.,  crystal- 
lized carbonate  of   soda   15   ozs.,  blue  vitriol  6.7  ozs.,  caustic 
soda  lye  of  16°  Be.  f  Ib. 

To  prepare  this  bath,  dissolve  the  tartar  and  the  crystallized 
carbonate  of  soda  in  ^  of  the  water,  and  the  blue  vitriol  in  the 
remaining  J^,  and  mix  both  solutions.  Filter  off  the  precipi- 
tate, dissolve  it  in  the  caustic  soda  lye,  and  add  this  solution  to 
the  other. 

This  bath  works  very  well,  and  may  be  recommended  to 
electro- platers  who  copper  zinc  exclusively,  but  where  all  kinds 
of  metals  are  to  be  coppered,  bath  No.  III.  is  to  be  preferred,  it 
yielding  equally  good  results  for  zinc. 

For  small  zinc  objects  which  are  to  be  coppered  in  a  sieve, 
bath  No.  III.  is  used,  it  being  heated  for  this  purpose,  and  a 
little  more  potassium  cyanide  added.  Roseleur  recommends 
for  the  same  purpose  a  bath  composed  as  follows: — 

V.  Water  10  quarts,  neutral  crystallized  bisulphite  of  soda 
i  y±  ozs.,  neutral  acetate  of  copper  8  ozs.,  75  per  cent,  potass- 
ium cyanide  I2j^  ozs.,  and  ammonia  y^  oz.     The  bath  is  pre- 
pared in  the  same  manner  as  formulae  I.  to  III. 

In  preparing  copper  baths,  the  acetate  of  copper  prescribed 
in  the  preceding  formulae  may  be  replaced  by  the  carbonate  or 
sulphate,  the  substitution  of  the  latter,  after  its  previous  con- 
version into  carbonate,  being  of  special  advantage  in  order  not 
to  impart  to  the  bath  too  great  a  resistance  by  the  potassium 
sulphate,  formed  by  reciprocal  decomposition.  The  following 
formula  is  especially  suitable  for  the  use  of  sulphate  of  copper 
(blue  vitriol)  : — 

VI.  Blue  vitriol     .         .         .         ....      10^  ozs. 

Crystallized  carbonate  of  soda         .         . 


Water     .         ^        ....         .  .10  quarts. 

Pulverized  bisulphite  of  soda .         .  .       7  ozs. 

Crystallized  carbonate  of  soda  .         ..  .       8^  ozs. 

98  to  99  per  cent,  potassium  cyanide  .       8}4     " 


DEPOSITION   OF   COPPER,  BRASS,  AND    BRONZE.  229 


First  dissolve  the  ioj^  ozs.  of  blue  vitriol  and  the  10%  ozs. 
of  crystallized  carbonate  of  soda,  each  by  itself,  in  hot  water, 
and  mix  the  two  solutions  ;  allow  the  precipitate  of  carbonate 
of  copper  to  settle,  and  pour  off  the  supernatant  clear  fluid. 
Then  pour  upon  the  precipitate  5  quarts  of  water,  add  the 
bisulphite  of  soda,  next  the  carbonate  of  soda,  and  mix  this 
solution  with  the  solution  of  the  potassium  cyanide  in  5  quarts 
of  water.  The  fluid  rapidly  becomes  clear  and  colorless,  when 
it  is  boiled  and  filtered. 

In  a  recent  formula  cuprous  oxide,  which  is  found  in  com- 
merce under  the  name  of  cupron,  is  used  in  place  of  cupric  oxides. 

VII.  Cupron  3^  ozs.,  99  per  cent,  potassium  cyanide  10^ 
ozs.,  pulverized  bisulphite  of  soda   lO^J  ozs.,  water   15  quarts. 

Dissolve  the  potassium  cyanide  in  one  half  the  prescribed 
quantity  of  water  (cold),  then  gradually  stir  in  the  cupron,  and 
after  the  solution  of  the  latter  add  the  bisulphite  of  soda  pre- 
viously dissolved  in  the  other  half  of  the  water. 

In  place  of  cupron,  cuproso-cupric  sulphite,  an  article 
patented  in  Germany,  may  be  used.  This  salt  dissolves  in 
potassium  cyanide  without  perceptible  evolution  of  cyanogen, 
since  it  contains  more  than  the  sufficient  quantity  of  sulphurous 
acid  than  is  required  for  the  reduction  of  the  oxide  salt  present. 
The  baths  prepared  with  cuproso-cupric  sulphite  can  be  pre- 
pared more  cheaply  than  baths  with  cupron. 

Suitable  formulae  for  baths  with  cuproso-cupric  sulphite  are 
as  follows  :  — 

VIII.  Ammonia-soda  if  ozs.,  99  per  cent,  potassium  cyanide 
8^2  ozs.,  cuproso-cupric  sulphite  4j^  ozs.,  water  10  quarts;   or, 

IX.  60  per  cent,  potassium   cyanide  14  ozs.,  cuproso-cupric 
sulphite  4*4  ozs.,  water  10  quarts. 

Dissolve  the  salts  in  the  order  given  in  5  quarts  of  the  water, 
stirring  constantly,  and  then  add  the  remaining  5  quarts  of 
water. 

Of  the  many  directions  for  copper  baths  without  potassium 
cyanide,  to  which  also  belongs  the  bath  prepared  according  to 
formula  IV.,  and  which  have  chiefly  been  proposed  for  copper- 


230  ELECTRO-DEPOSITION   OF   METALS. 

ing  cast  and  wrought  iron,  only  a  few  need  be  mentioned  as 
being  actually  available. 

Weil  obtains  a  deposit  of  copper  in  a  bath  consisting  of  a 
solution  of  blue  vitriol  in  an  alkaline  solution  of  tartrate  of  potas- 
sium or  sodium.  Such  a  bath  is  composed  as  follows: — 

X.  Water  10  quarts,  potassium  sodium  tartrate  (Rochelle 
salt)  53  ozs.,  blue  vitriol  10^  ozs.,  60  per  cent,  caustic  soda 
28  ozs. 

The  chief  purpose  of  the  large  content  of  caustic  soda  is  to 
keep  the  tartrate  of  copper,  which  is  almost  insoluble  in  water, 
in  solution.  According  to  Weil,  the  coppering  may  be  execu- 
ted in  three  different  ways,  as  follows : — 

The  iron  articles  tied  to  zinc  wires  or  in  contact  with  zinc 
strips  are  brought  into  the  bath ;  the  coppering  thus  taking 
place  by  contact.  Or,  porous  clay  cells  are  placed  in  the  bath 
containing  the  articles ;  these  clay  cells  are  filled  with  soda  lye 
in  which  zinc  plates  connected  with  the  object-rods  are  allowed 
to  dip,  the  arrangement  in  this  case  forming  an  element  with 
which,  by  the  solution  of  the  zinc  in  the  soda  lye,  a  current  is 
produced,  which  effects  the  decomposition  of  the  copper  solu- 
tion and  the  deposition.  When  saturated  with  zinc  the  soda 
lye  becomes  ineffective,  and,  according  to  Weil,  it  may  be  re- 
generated by  the  addition  of  sodium  sulphide,  which  separates 
the  dissolved  zinc  as  zinc  sulphide.  The  third method of 'copper- 
ingconsists  in  the  use  of  the  current  of  a  battery  or  of  a  dynamo- 
machine,  in  which  case  copper  anodes  have,  of  course,  to  be 
employed. 

A  copper  bath  recommened  by  Walenn  is  composed  of  a 
solution  of  equal  parts  of  tartrate  of  ammonia  and  potassium 
cyanide,  in  which  3  to  5  per  cent,  of  copper  (in  the  form  of 
blue  vitriol  or  moist  cupric  hydrate)  is  dissolved.  The  bath  is 
to  be  heated  to  about  140°  F. 

Copper  bath  according  to  Pfanhauser. — Dissolve  2  ^  ozs.  of 
cyanide  of  copper,  i^j  drachms  each  of  pure  100  per  cent, 
potassium  cyanide  and  crystallized  sal  ammoniac,  and  5^ 
drachms  of  ammonia  soda  in  I  quart  of  lukewarm  water,  stirring 
constantly  until  all  the  salts  are  dissolved. 


DEPOSITION   OF   COPPER,  BRASS,  AND   BRONZE.  231 

The  temperature  of  the  bath  should  be  between  68°  and  77° 
F.,  and  the  strength  of  current  3  volts.  Density  of  current  0.5 
ampere.  In  case  the  bath  should  become  poor  in  metal, 
cyanide  of  copper  has  to  be  added.  When  the  copper  anodes 
become  coated  with  too  great  an  abundance  of  green  slime, 
which  does  not  decrease  during  the  night  when  the  bath  is  not 
working,  some  potassium  cyanide,  about  J^  drachm  per  quart, 
should  be  added. 

Gauduin's  copper  bath  consists  of  a  solution  of  oxalate  of 
copper  with  oxalate  of  ammonia  and  free  oxalic  acid.  Fon- 
taine asserts  that  the  bath  works  well,  when  heated  to  between 
140°  and  150°  F. 

Copper  baths  containing  cyanide  cannot  be  brought  into 
pitched  vats,  vats  of  stoneware  or  enameled  iron  being  used  for 
smaller  baths,  and  for  larger,  basins  of  brick  set  in  cement,  or 
iron  reservoirs  lined  with  ebonite.  For  large  baths  containing 
potassium  cyanide  wooden  vats  lined  with  lead  can  be  used 
without  disadvantage,  since  a  slight  coating  of  cyanide  of  lead, 
which  may  be  formed  upon  the  lead,  is  insoluble  in  potassium 
cyanide,  and  even  if  a  small  quantity  of  cyanide  of  lead  would 
be  dissolved  in  the  bath  by  the  presence  of  organic  acids,  a 
separation  of  lead  besides  copper  upon  the  cathodes  does  not 
take  place. 

Execution  of  coppering. — The  general  rules  given  under  nickel- 
ing, as  regards  the  suitable  composition  of  the  bath,  correct 
selection  of  anodes,  careful  scouring  and  pickling  of  the  objects 
and  proper  current-strength  also  apply  to  coppering. 

Annealed  sheets  of  pure  copper  with  as  large  a  surface  as 
possible  serve  as  anodes.  In  all  baths  containing  cyanide  the 
anodes  become,  in  a  comparatively  short  time,  coated  with  a 
greenish  slime  consisting  of  a  basic  copper  cyanide  mostly 
soluble  in  excess  of  potassium  cyanide.  When  a  very  thick 
formation  of  such  slime  takes  place,  potassium  cyanide  is  want- 
ing, and  has  to  be  added.  Other  phenomena  appearing  in 
copper  baths  containing  cyanide  may  as  well  here  be  men- 
tioned. Too  large  an  excess  of  potassium  cyanide  causes  a 


232  ELECTRO-DEPOSITION    OF   METALS. 

strong  evolution  of  hydrogen  bubbles  on  the  objects ;  but  no 
deposition  of  copper,  or  only  a  slight  one,  takes  place,  which 
besides  has  the  tendency  to  peel  off.  If  this  phenomenon  ap- 
pears after  adding  potassium  cyanide,  the  excess  can  be  readily 
removed  by  the  addition  of  copper  salt,  best  cyanide  of  copper, 
stirred  with  a  small  quantity  of  the  bath  to  a  thinly  fluid  paste 
and  added  to  the  bath  with  constant  and  long-continued  stirring. 
After  each  addition,  a  test  is  made  whether  an  object  suspended 
in  the  bath  is  rapidly  and  regularly  coppered ;  if  such  is  not 
the  case,  the  addition  of  cyanide  of  copper  is  repeated  until 
the  bath  works  in  a  faultless  and  correct  manner.  On  the  other 
Kand,  a  deposit  may  not  be  formed  for  the  want  of  potassium 
cyanide,  which  is  already  indicated  by  a  thick  formation  of  slime 
on  the  anodes,  and  by  the  fluid  acquiring  a  pale  blue  color;  or 
the  metallic  content  of  the  bath  may  be  too  small.  While  in 
the  first  case  a  slight  addition  of  potassium  cyanide  alone  will 
cause  the  bath  to  work  correctly,  in  the  other  case,  an  addition 
of  solution  of  copper  cyanide  in  potassium  cyanide  is  required 
to  augment  the  content  of  metal  in  the  bath,  it  being  best  to 
introduce  together  with  the  metallic  cyanide  solution  a  small 
quantity  of  carbonate  and  bisulphite  of  soda,  in  order  to  de- 
crease the  resistance  to  conductivity.  In  place  of  solution  of 
copper  cyanide  in  potassium  cyanide,  commercial  crystallized 
potassium  copper  cyanide  may  be  used.  In  coppering  with  a 
strong  current  the  anodes  become  frequently  coated  to  such 
an  extent  that  finally  no  current  passes  into  the  bath,  the  ex- 
cess of  potassium  cyanide  being  unable  to  dissolve  the  copper 
cyanide  as  rapidly  as  it  is  formed.  In  this  case  scouring  the 
anodes  is  the  only  remedy. 

Many  platers  are  of  the  opinion  that  the  articles  to  be 
coppered  do  not  require  very  careful  cleaning  and  pickling  be- 
fore plating  because  the  copper  bath  containing  potassium 
cyrnide  as  well  as  copper  baths  with  alkaline-organic  combina- 
tions sufficiently  effect  the  cleansing  and  pickling.  This  opin- 
ion, however,  is  wrong.  It  is  true  the  potassium  cyanide  dis- 
solves a  layer  of  oxide,  but  not  or  at  least  very  incompletely 


DEPOSITION    OF   COPPER,  BRASS,  AND    BRONZE.  233 

any  grease  present  upon  the  articles,  and  hence  it  advisable  to 
free  articles  intended  for  coppering  as  thoroughly  from  grease 
as  articles  to  be  nickeled. 

The  preliminary  scouring  and  pickling  of  the  articles  to  be 
coppered  are  executed  according  to  the  directions  given  on 
page  156.  The  same  precautions  discussed  under  nickeling 
have  to  be  used  in  suspending  the  objects  in  the  bath,  and  the 
directions  given  there  for  the  suitable  arrangement  of  the 
anodes,  etc.,  also  apply  to  coppering;  however,  a  copper  bath 
conducting  better  than  a  nickel  bath,  the  distance  between  the 
anodes  and  the  objects  may,  if  necessary,  be  somewhat  greater. 

With  a  proper  arrangement  of  the  anodes  and  correct  regu- 
lation of  the  current,  the  objects  should  be  entirely  coated  with 
copper  in  a  few  minutes  after  being  hung  in  the  bath.  In  five 
to  ten  minutes  the  objects  are  taken  from  the  bath  and  brushed 
with  a  scratch-brush  of  not  too  hard  brass  wires,  whereby  the 
deposit  should  everywhere  show  itself  to  be  durable  and  ad- 
herent. Defective  places  are  especially  thoroughly  scratch- 
brushed,  scoured,  and  pickled  ;  the  objects  are  then  returned 
to  the  bath.  For  solid  and  heavy  coppering  the  objects  remain 
in  the  bath  until  the  original  lustre  and  red  tone  of  the  copper- 
ing disappear  and  pass  into  a  dull  discolored  brown ;  at  this 
stage  the  objects  are  again  scratch-brushed  until  they  show 
lustre  and  the  red  copper  color,  whereby  it  is  of  advantage  to 
moisten  them  with  tartar  water.  They  are  then  again  returned 
to  the  bath,  where  they  remain  until  the  dull  discolored  tone 
reappears.  They  are  then  taken  out,  scratch-brushed  bright, 
rinsed  in  several  clean  waters,  plunged  into  hot  water,  and  finally 
dried,  first  in  sawdust  and  then  thoroughly,  at  a  high  tempera- 
ture, in  the  drying  chamber.  Special  attention  must  be  paid  to 
the  thorough  washing  of  the  coppered  objects,  because,  if  any- 
thing of  the  bath  containing  cyanide  remains  in  the  depressions 
or  pores,  small,  dark,  round  stains  appear  on  those  places, 
which  cannot  be  removed,  or  at  least  only  with  great  difficulty, 
they  reappearing  again  in  a  short  time  after  having  been  ap- 
parently removed.  This  formation  of  stains  appears  especially 


234          ELECTRO- DEPOSITION  OF  METALS. 

frequently  upon  coppered  (as  well  as  brassed)  iron  and  zinc 
castings,  which  cannot  be  produced  without  pores.  To  prevent 
the  formation  of  these  stains  the  following  method  is  recom- 
mended :  Since  the  rinsing  in  many  waters,  and  even  allowing 
the  objects  to  lie  for  hours  in  running  water,  offer  no  guarantee 
that  every  trace  of  fluid  containing  cyanide  has  been  removed, 
the  objects  are  brought  into  a  slightly  acid  bath  which  de- 
composes the  fluid,  a  mixture  of  I  part  of  acetic  acid  and  50 
parts  of  water  being  well  adapted  for  the  purpose.  The  objects 
are  allowed  to  remain  in  this  mixture  for  three  to  five  minutes, 
when  they  are  rinsed  off  in  water  and  dipped  for  a  few  minutes 
in  dilute  milk  of  lime.  They  are  finally  rinsed  off  and  dried. 
Coppered  castings  thus  treated  will  show  no  stains. 

O.  Shultz  obtained  a  patent  for  the  following  method  for  re- 
moving the  hydrochloric  acid  from  the  pores,  and  thus  prevent- 
ing the  formation  of  stains :  The  plated  objects  are  placed  in  a 
room  which  can  be  hermetically  closed.  The  air  is  then  re- 
moved from  the  room  by  the  introduction  of  steam  of  a  high 
tension,  and  by  means  of  an  air-pump,  and  water  sprinkled 
upon  the  objects.  By  this  treatment  in  vacuum  the  fluid  in  the 
pores  comes  to  the  surface  and  the  salt  solution  is  removed  by 
the  water  sprinkled  over  the  articles. 

After  drying,  the  deposit  of  copper,  if  it  is  to  show  high 
lustre,  is  polished  with  soft  wheels  of  fine  flannel  and  dry  Vienna 
lime ;  commercial  polishing  red  FFF,  moistened  with  a  little 
alcohol,  is  also  an  excellent  polishing  agent  for  copper  and  all 
other  soft  metals. 

As  is  well  known,  massive  copper  rapidly  oxidizes  in  a  humid 
atmosphere,  and  this  is  the  case  to  a  still  greater  extent  with 
electro-deposited  copper.  Hence,  the  coppered  objects,  if  they 
are  not  to  be  further  coated  with  a  non-oxidizing  metal,  have 
to  be  provided  with  a  colorless,  transparent  coat  of  lacquer  (see 
"  Lacquering"). 

It  frequently  happens  that  slightly  coppered  (as  well  as 
slightly  brassed)  objects,  especially  of  zinc,  after  some  time,  be- 
come entirely  white  and  show  no  trace  of  the  deposit.  This  is 


DEPOSITION    OF   COPPER,  BRASS,  AND    BRONZE.  235 

due  to  the  deposit  penetrating  into  the  basis-metal,  as  already 
explained.  Lacquering  in  this  case  is  of  no  avail,  the  deposit 
also  disappearing  under  the  coat  of  lacquer.  The  only  remedy 
against  this  phenomenon  is  a  heavier  deposit. 

If  the  coppered  objects  are  to  be  coated  with  another  metal, 
drying  is  omitted,  and  after  careful  rinsing  they  are  directly 
brought  into  the  respective  bath,  or  into  thequicking  pickle,  if, 
as,  for  instance,  in  silvering,  quicking  has  to  be  done.  In  such 
cases,  where  the  copper  deposit  serves  only  as  an  intermediary 
for  the  reception  of  another  metallic  coating,  the  objects  need  not 
to  be  coppered  as  thickly,  as  previously  described,  by  treating 
them  three  times  in  the  bath.  Preliminary  coppering  for  5  to 
10  minutes  suffices  in  all  cases,  which  is  succeeded  by  scratch- 
brushing  in  order  to  be  convinced  that  the  deposit  adheres 
firmly  and  that  the  basis-metal  is  uniformly  coated.  The  ob- 
jects are  then  hung  in  the  bath  for  5  to  10  minutes  longer  with 
a  weak  current.  In  coppering  sheet  iron  or  sheet  zinc  which  is 
to  be  nickeled,  the  sheets  are  taken  from  the  bath  after  3  to  5 
minutes,  at  any  rate  while  they  still  retain  their  lustre,  scratch- 
brushing  being  in  this  case  omitted.  For  coppering  such  sheets 
a  current-density  of  0.5  ampere  with  a  tension  of  3.5  to  4  volts 
is  required.  The  treatment  of  copper  baths,  when  they  be- 
come inactive  or  exhibit  other  abnormal  phenomena,  has  been 
referred  to  on  p.  194;  all  other  rules  for  galvanic  baths  given 
in  Chap.  VI.  must  here  also  be  observed. 

For  coppering  small  articles  en  masse  in  sieves  it  is  recom- 
mended to  have  the  copper  baths  right  hot ;  for  the  rest,  the 
process  is  the  same  as  that  given  for  nickeling  small  articles  en 
masse. 

Coppering  by  contact  arid  dipping. — According  to  Liidersdorff, 
a  solution  of  tartrate  of  copper  in  neutral  potassium  tartrate 
serves  for  this  purpose.  A  suitable  modification  of  this  bath  is 
as  follows:  Heat  10  quarts  of  water  to  140°  F.,  add  2  Ibs.  of 
pulverized  tartar  (cream  of  tartar)  free  from  lime,  and  10^  ozs. 
of  carbonate  of  copper.  Keep  the  fluid  at  the  temperature 
above  mentioned  until  the  evolution  of  gas  due  to  the  decom- 


236  ELECTRO-DEPOSITION   OF   METALS. 

position  of  the  carbonate  of  copper  ceases,  and  then  add  in 
small  portions,  and  with  constant  stirring,  pure  whiting  until 
effervescence  is  no  longer  perceptible.  Filter  off  the  fluid  from 
the  tartrate  of  lime,  separate  and  wash  the  precipitate  so  that 
the  filtrate,  inclusive  of  the  wash  water,  amounts  to  10  or  12 
quarts. 

Zinc  is  coppered  in  this  bath  by  simple  immersion  ;  other 
metals  have  to  be  brought  in  contact  with  zinc. 

To  coat  zinc  plates  with  a  very  thin  but  hard  layer  of  copper, 
immerse  the  plates  in  a  bath  composed  of  100  parts  of  water 
saturated  with  cupric  chloride — cupric  chloride  40  parts,  water 
60 — 150  parts  of  ammonia  and  3000  parts  of  water.  For  very 
solid  coppering,  the  above-described  bath,  which  is  of  a  beautiful 
blue  color,  is  used,  and  a  saturated  solution  of  potassium 
cyanide  in  water  added  until  the  blue  of  the  first  mixture  has 
quite  disappeared.  For  plates  engraved  with  the  burin  or  for 
stamped  plates,  it  is  best  to  use  a  mixture  of  cyanide  of  copper 
with  neutral  potassium  sulphate,  to  which  is  added  a  mixture  of 
a  saturated  solution  of  blue  vitriol  in  water  and  of  water  satur- 
ated with  cyanide  of  copper.  The  bath  is  ready  for  use  when 
the  precipitate  is  completely  dissolved  and  the  fluid  entirely 
discolored. 

Another  contact  coppering  bath  is  that  prepared  according 
to  formula  X.,  proposed  by  Weil.  In  this  bath  zinc  is  also 
coppered  by  simple  immersion,  and  copper  and  iron  in  con- 
tact with  zinc  strips. 

According  to  Bacco,  a  copper  bath  in  which  zinc  may  be 
coppered  by  immersion,  and  iron  and  other  metals  in  contact 
with  zinc,  is  prepared  by  adding  to  a  saturated  solution  of  blue 
vitriol,  potassium  cyanide  solution  until  the  precipitate  of 
cyanide  of  copper  which  is  formed  is  again  dissolved.  Then 
add  TV  to  \  of  the  volume  of  liquid  ammonia  and  dilute  with 
water  to  8°  Be. 

The  so-called  brush-coppering  which  has  been  recommended 
may  here  be  mentioned.  This  process  may  be  of  practical 
advantage  for  coppering  very  large  objects  which  by  another 


DEPOSITION    OF    COPPER,  BRASS,  AND    BRONZE.  237 

method  could  only  be  coated  with  difficulty.  The  deposit 
of  copper  is,  of  course,  very  thin.  The  process  is  executed 
as  follows :  The  utensils  required  are  two  vessels  of  sufficient 
size,  each  provided  with  a  brush,  preferably  so  wide  that  the 
entire  surface  of  the  object  to  be  treated  can  be  coated  with 
one  application.  One  of  the  vessels  contains  a  strongly  satu- 
rated solution  of  caustic  soda,  and  the  other  a  strongly  satu- 
rated solution  of  blue  vitriol.  For  coppering,  the  well-cleansed 
object  is  first  uniformly  coated  with  a  brushful  of  the  caustic 
soda  solution,  and  then  also  with  a  brushful  of  the  blue  vitriol 
solution.  A  quite  thick  film  of  copper  is  immediately  deposited 
upon  the  object.  Care  must  be  had  not  to  have  the  brush  too 
full  and  not  to  touch  the  places  once  gone  over  the  second 
time,  as  otherwise  the  layer  of  copper  does  not  adhere  firmly. 

Many  iron  and  steel  objects  are  provided  with  a  thin  film  of 
copper  in  order  to  give  them  a  more  pleasing  appearance.  For 
this  purpose  a  copper  solution  of  10  quarts  of  water,  I  ^  ozs.  of 
blue  vitriol,  and  I  ^  ozs.  of  pure  concentrated  sulphuric  acid 
may  be  used.  Dip  the  iron  or  steel  objects,  previously  freed 
from  grease  and  oxide,  for  a  moment  in  the  solution,  moving 
them  constantly  to  and  fro ;  then  rinse  them  immediately  in 
ample  water,  and  dry.  By  keeping  the  articles  too  long  in  the 
solution,  the  copper  separates  in  a  pulverulent  form  and  does 
not  adhere. 

Steel  pens,  needles'  eyes,  etc.,  may  be  coppered  by  diluting 
the  copper  solution  just  mentioned  with  double  the  quantity  of 
water,  moistening  sawdust  with  the  solution  and  revolving  the 
latter,  together  with  the  articles  to  be  coppered,  in  a  wooden 
tumbling  box  (p.  129). 

The  inlaying  of  depressions  of  coppered  art-castings  with 
black  may  be  done  in  different  ways.  Some  blacken  the  ground 
by  applying  a  mixture  of  spirit  lacquer  with  lampblack  and 
graphite,  while  others  use  oil  of  turpentine  with  lampblack  and 
a  few  drops  of  copal  lacquer.  A  very  thin  nigrosin  lacquer 
mixed  with  finely  pulverized  graphite  is  very  suitable  for  the 
purpose.  When  the  lacquer  is  dry  the  elevated  places  which 


238  ELECTRO-DEPOSITION    OF    METALS. 

are  to  show  the  copper  color  are  cleansed  with  a  linen  rag 
moistened  with  alcohol. 

Electrolytically  coppered  articles  may  be  inlaid  black  by 
coating  them,  after  thorough  scouring  and  pickling,  with  arsenic 
in  one  of  the  baths  given  under  "  Electro-deposition  of  Arsenic," 
and,  after  drying  in  hot  water  and  sawdust,  freeing  the  surfaces 
and  profiles,  which  are  to  appear  coppered,  from  the  coating  of 
arsenic  by  polishing  upon  a  felt  wheel.  If  this  polishing  is  to 
be  avoided,  the  portions  which  are  not  to  be  black  may  be 
coated  with  stopping-off  varnish,  and  arsenic  deposited  upon 
the  places  remaining  free. 

For  coloring,  platinizing,  and  oxidizing  of  copper,  see  the 
proper  chapter. 

2.    Brassing  (  Cuivre-poli  Deposit) . 

Brass  is  an  alloy  of  copper  and  zinc  whose  color  depends  on 
the  quantitative  proportions  of  both  metals.  The  alloys  known 
as  yellow  brass ',  red  brass  (similor,  tombac},  consist  essentially 
of  copper  and  zinc,  while  those  known  as  bell  metal,  gun  metal, 
and  the  bronzes  of  the  ancients  are  composed  of  copper  and  tin. 
Modern  bronzes  contain  copper,  zinc,  and  tin. 

The  behavior  of  brass  towards  acids  is  nearly  the  same  as 
that  of  copper ;  'it  oxidizes,  however,  less  readily  in  the  air,  is 
harder  than  copper,  malleable,  and  can  be  rolled  and  drawn 
into  wire. 

Brass  baths. — According  to  the  plan  pursued  in  this  work, 
only  the  most  approved  formulae  will  be  given.  There  exist 
a  large  number  of  directions  for  brass  baths ;  but  we  share  the 
opinion  of  Roseleur,  that  a  brass  bath  containing  copper  and  zinc 
salts  in  nearly  equal  proportions  is  the  most  suitable  and  least 
subject  to  disturbances.  A  brass  bath  is  to  be  considered  as  a 
mixture  of  solutions  of  cyanide  of  copper  and  cyanide  of  zinc, 
or  of  other  copper- zinc  salts  in  the  most  suitable  solvent;  and 
since  a  solution  of  cyanide  of  copper  requires  a  different  current- 
strength  from  one  of  zinc  salt,  it  will  be  seen  that  according  to 
the  greater  or  smaller  current-strength,  now  more  of  the  one, 


DEPOSITION    OF    COPPER,  BRASS,  AND   BRONZE.  239 

and  now  more  of  the  other  metal  is  deposited,  which,  of  course, 
influences  the  color  of  the  deposit.  Hence  the  proper  regula- 
tion of  the  current  is  the  chief  condition  for  obtaining  beauti- 
ful deposits,  let  the  bath  be  composed  as  it  may. 

For  all  baths  containing  more  than  one  metal  in  solution,  it 
may  be  laid  down  as  a  rule  that  the  less  positive  metal  is  first 
deposited.  In  a  brass  bath  copper  is  the  negative  and  zinc  the 
positive  metal ;  and  hence  a  weaker  current  deposits  more 
copper,  in  consequence  of  which  the  deposit  becomes  redder, 
while,  vice  versa,  a  more  powerful  current  decomposes  besides 
the  copper  solution  also  a  larger  quantity  of  zinc  solution  and 
reduces  zinc,  the  color  produced  being  more  pale  yellow  to 
greenish.  By  bearing  this  in  mind  it  is  not  difficult  to  ob- 
tain any  desired  shades  within  certain  limits. 

I.  Brass  bath  according  to  Roselenr. — Blue  vitriol  and  zinc 
sulphate  (white  vitriol),  of  each  5^  ounces,  and  crystallized 
carbonate  of  soda  15^  ounces.  Crystallized  carbonate  of  soda 
and  crystallized  bisulphite  of  soda,  of  each  7  ounces,  98  per 
cent,  potassium  cyanide  8^  ounces,  arsenious  acid  30^  grains, 
water  10  quarts. 

The  bath  is  prepared  as  follows :  In  5  quarts  of  warm  water 
dissolve  the  blue  vitriol  and  the  zinc  sulphate ;  and  in  the  other 

5  quarts  the  15^  ounces  of  carbonate  of  soda;   then  mix  both 
solutions,  with  stirring.     A  precipitate  of  carbonate  of  copper 
and  carbonate  of  zinc  is  formed,  which   is   allowed   quietly  to 
settle  for  i o  to  12  hours,  when  the   supernatant  clear  fluid  is 
carefully  poured  off,  so  that  nothing  of  the  precipitate  is  lost. 
Washing  the  precipitate  is  not  necessary ;   the  clear  fluid  poured 
off  is  of  no  value  and  is  thrown  away.     Now  add  to  the  preci- 
pitate so  much  water  that  the  resulting  fluid  amounts  to  about 

6  quarts,  and  dissolve  in  it,  with  constant  stirring,  the  carbonate 
and  bisulphite  of  soda,  adding  these  salts,  however,  not  at  once, 
but  gradually,  in  small  portions,  to  avoid  foaming  over  by  the 
escaping  carbonic  acid.     Dissolve  the  potassium  cyanide  in  4 
quarts  of  cold  water  and  add  this  solution,  with  the  exception 
of  about  y?,  pint,  in  which  the  arsenious  acid  is  dissolved  with 


240  ELECTRO- DEPOSITION   OF   METALS. 

the  assistance  of  heat,  to  the  first  solutions,  and  finally  add  the 
solution  of  arsenious  acid  in  the  j£  pint  of  water  retained,  when 
the  bath  should  be  clear  and  colorless.  If  after  continued  stir- 
ring, particles  of  the  precipitate  remain  undissolved,  carefully 
add  somewhat  more  potassium  cyanide  until  solution  is  com- 
plete. 

Fresh  brass  baths  work,  as  a  rule,  more  irregularly  than  any 
other  baths  containing  cyanide,  the  deposit  being  either  too  red 
or  too  green  or  gray,  while  frequently  one  side  of  the  object  is 
coated  quite  well,  and  the  other  not  at  all.  To  force  the  bath 
to  work  correctly  it  must  be  thoroughly  boiled,  the  water  which 
is  lost  by  evaporation  being  replaced  by  the  addition  of  dis- 
tilled water  or  pure  rain  water.  If  boiling  is  to  be  avoided,  the 
bath,  as  previously  mentioned,  is  worked  through  for  hours,  and 
even  for  days,  with  the  current,  until  an  object  suspended  in  it 
is  correctly  brassed. 

The  addition  of  a  small  quantity  of  arsenious  acid  is  claimed 
to  make  the  brassing  brighter ;  but  the  above  mentioned  pro- 
portion of  30^  grains  for  a  lO-quart  bath  must  not  be  ex- 
ceeded, as  otherwise  the  color  of  the  deposit  would  be  too  light 
and  show  a  gray  tone. 

II.  Crystallized  carbonate  of  soda  10^  ounces,  crystallized 
bisulphite  of  soda  7  ounces,  neutral  acetate  of  copper  4.4 
ounces,  crystallized  chloride  of  zinc  4.4  ounces,  98  per  cent, 
potassium  cyanide  14.11  ounces,  arsenious  acid  30^  grains, 
water  10  quarts. 

The  preparation  of  this  bath  is  more  simple  than  that  of  the 
preceding. 

Dissolve  the  carbonate  and  bisulphite  of  soda  in  4  quarts  of 
water,  then  mix  the  acetate  of  copper  and  chloride  of  zinc  with 
2  quarts  of  water,  and  gradually  add  this  mixture  to  the  solu- 
tion of  the  soda  salts.  Next  dissolve  the  potassium  cyanide  in 
4  quarts  of  water,  and  add  this  solution  to  the  first,  retaining, 
however,  a  small  portion  of  it,  in  which  dissolve  the  arsenious 
acid  with  the  assistance  of  heat.  Finally  add  the  arsenious 
acid  solution,  when  the  bath  will  become  clear.  Boiling  the 
bath,  or  working  it  through  with  the  current,  is  also  required. 


DEPOSITION    OF   COPPER,  BRASS,  AND    BRONZE.  241 

For  brassing  iron  in  this  bath  the  addition  of  carbonate  of 
soda  may  be  increased  up  to  35  ounces  for  a  lo-quart  bath, 
this  being  also  permissible  when  frequent  scratch-brushing  is 
to  be  avoided  in  coating  zinc  articles  with  a  heavy  deposit  of 
brass ;  because  it  seems  that  a  large  content  of  carbonate  of 
soda  in  the  bath  considerably  retards  the  changing  of  the  brass 
color  into  a  discolored  brown,  though  the  brilliancy  of  the  de- 
posit appears  to  suffer  somewhat.  When  boiled  from  I  to  2 
hours,  or  worked  through  with  the  current  for  10  to  12  hours, 
the  bath  prepared  according  to  formula  II.  works  very  well ;  it 
requires  a  current  of  0.5  to  0.55  ampere,  with  a  tension  of  3.5 
to  4  volts  per  I$j4  square  inches  surface. 

The  same  as  for  copper  baths,  cuproso-cupric  sulphite  may 
also  be  advantageously  used  for  the  preparation  of  brass  baths, 
a  suitable  formula  being  as  follows : 

III.  Pure   crystallized  sulphate  of  zinc  (zinc  vitriol  or  white 
vitriol)  5  ^  ozs.,  crystallized  carbonate  of  soda  7  ^  ozs.     Neutral 
crystallized  bisulphite  of  soda  9^  ozs.,  ammonia-soda  \y2  ozs., 
99  per  cent,  potassium  cyanide  3  ozs.,  cuproso-cupric  sulphite  3 
ozs.,  water  10  quarts. 

The  bath  is  prepared  as  follows :  Dissolve  the  sulphate  of 
zinc  in  5  quarts  of  the  water,  the  carbonate  of  soda  in  4  quarts  of 
warm  water,  and  mix  the  two  solutions.  After  complete  settling 
of  the  precipitate  of  carbonate  of  zinc  formed,  siphon  off  the 
supernatant  clear  fluid  as  much  as  possible,  add  5  quarts  of 
water  and  then  the  ammonia-soda.  In  the  other  5  quarts  of 
water  dissolve  the  potassium  cyanide  and  the  neutral  bisulphite 
of  soda,  and  when  solution  is  complete  add  this  solution  to  the 
first,  when  by  vigorous  stirring  the  carbonate  of  zinc  will  also 
dissolve. 

This  bath  yields  beautiful  pale  yellow  deposits  of  a  warm 
brass  tone. 

IV.  Crystallized   carbonate  of  soda    10^    ozs.,   crystallized 
bisulphite  of  soda  7  ozs.,  cyanide  of  copper  and  cyanide  of  zinc 
of  each  3J^   ozs.,  water   10  quarts,  and  enough  98  per  cent, 
potassium  cyanide  to  render  the  solution  clear. 

16 


242  ELECTRO-DEPOSITION    OF   METALS. 

To  prepare  the  bath  dissolve  the  carbonate  and  bisulphite  of 
soda  in  2  to  3  quarts  of  water,  rub  in  a  porcelain  mortar  the 
cyanide  of  copper  and  cyanide  of  zinc  with  a  quart  of  water  to 
a  thin  paste,  add  this  paste  to  the  solution  of  the  soda  salts,  and 
finally  add,  with  vigorous  stirring,  concentrated  potassium  cyan- 
ide solution  until  the  metallic  cyanides  are  dissolved.  Dilute 
the  volume  to  10  quarts,  and,  for  the  rest,  proceed  as  given  for 
formulae  I.  and  II. 

For  brassing  zinc  exclusively,  Roseleur  recommends  the  fol- 
lowing bath : — 

V.  Dissolve  9^  ozs.  of  crystallized  bisulphite  of  soda  and  14 
ozs.  of  70  per  cent,  potassium  cyanide  in  8  quarts  of  water,  and 
add  to  this  solution  one  of  4^  ozs.  each  of  neutral  acetate  of 
copper    and    crystallized   chloride   of    zinc,    5^   ozs.   of   aqua 
ammonia,  and  2  quarts  of  water. 

For  brassing  cast-iron,  wr ought-iron,  and  steel,  Gore  highly 
recommends  the  following  composition: — 

VI.  Dissolve  35  ^  ozs.  of  crystallized  carbonate  of  soda,   7 
ozs.  of  crystallized  bisulphite  of  soda,  13^   ozs.  of  98  per  cent, 
potassium  cyanide  in   8  quarts  of  water;   then  add,  with   con- 
stant stirring,  a  solution  of  fused   chloride  of  tin  3^  ozs.,  and 
neutral  acetate  of  copper  4^   ozs.,  in  2  quarts  of  water.     Boil 
and  filter.     This  bath  works  best  with  a  current  of  3.75  volts. 

According  to  Norris  and  Johnson,  a  good  brass  bath  is  said 
to  be  obtained  as  follows :  — 

VII.  Carbonate  of  ammonia  35 J^  ozs.,  70  per  cent,  potassium 
cyanide  35  ]/^  ozs.,  cyanide  of  copper  and  cyanide  of  zinc,  each 
2j{  ozs.,  water  10  quarts. 

The  large  content  of  potassium  cyanide  in  this  bath  is  unin- 
telligible. 

A  solution  for  transferring  any  copper- zinc  alloy  serving  as 
anode  is  composed,  according  to  Hess,  as  follows:  — 

VIII.  Bisulphite  of  soda  14^  ozs.,  crystallized  sal  ammoniac 
9*4  ozs.,  98  per  cent,  potassium  cyanide  2^/2    ozs.,  water   10 
quarts. 

Cast  metal  plates  are  to  be  used  as  anodes.     The  transfer 


DEPOSITION    OF    COPPER,  BRASS,  AND    BRONZE.  243 

begins  after  a  medium  strong  current  has,  for  a  few  hours, 
passed  through  the  bath.  This  bath  is  also  well  adapted  for 
the  deposition  of  tombac,  with  the  use  of  tombac  anodes ;  and 
the  most  suitable  tension  of  the  current  is  3  to  3.5  volts. 

IX.  For  brassing  all  kinds  of  metals  Wm.  Pfanhauser,  of 
Vienna,  recommends  the  following  bath:  — 

Dissolve  1 1/2,  ozs.  each  of  cyanide  of  copper  and  cyanide  of 
zinc,  1 1/6  drachms  of  pure  looper  cent,  potassium  cyanide,  il/& 
drachms  of  crystallized  sal  ammoniac,  and  5  */2  drachms  of  am- 
monia-soda in  I  quart  of  lukewarm  water,  stirring  constantly 
until  all  the  salts  are  dissolved.  The  bath  is  ready  for  imme- 
diate use,  and  does  not  requfre  boiling  or  previous  working 
through  with  the  current. 

The  temperature  of  the  bath  should  be  between  68°  and  77° 
F.  For  brassing  zinc  the  current  should  have  a  strength  of  2^ 
volts,  for  iron  3  volts,  for  chains  3  to  3^  volts,  and  for  small 
articles  en  masse  4  volts.  Density  of  the  current,  0.5  ampere. 

From  the  composition  of  this  bath  it  will  be  seen  that  it  con- 
tains quite  a  large  content  of  metal,  i^  ozs.  of  cyanide  of 
copper  being  equal  to  about  6^  drachms  of  copper,  and  \y2 
ozs.  of  cyanide  of  zinc  to  about  5j£  drachms  of  zinc.  Hence 
the  bath  contains  about  12*^  drachms  of  brass  per  quart. 

Brassing  in  this  bath  succeeds  equally  well  with  all  kinds  of 
metals,  the  result  being  a  uniform  deposit  of  metal  while  the 
color,  even  of  thick  deposits,  is  a  fiery  sad  yellow.  Small  articles, 
which  are  suspended  en  masse  in  dipping  baskets,  as  well  as  steel 
chains,  and  even  cast-iron,  which  is  notoriously  difficult  to  brass, 
become  rapidly  coated  in  this  bath.  In  case  the  brass  anodes 
become  coated  with  too  great  an  abundance  of  green  slime, 
which  decreases  during  the  night  when  the  bath  is  not  working, 
some  potassium  cyanide,  about  I  J^  drachms  per  quart,  should 
be  added.  Of  course,  the  bath  must  be  supplied  from  time  to 
time  with  additions  of  fresh  cyanide  of  copper  and  cyanide  of 
zinc. 

Execution  of  brassing. — The  most  suitable  density  of  current 
for  brassing  is  0.6  to  0.7  ampere  at  3  to  4  volts. 


244  ELECTRO-DEPOSITION    OF   METALS. 

As  previously  mentioned,  the  color  of  the  deposits  depends 
on  the  proportional  quantity  in  which  copper  and  zinc  are 
present,  a  strong  current  depositing  more  zinc  and  a  weak  cur- 
rent more  copper.  By  diminishing  or  increasing  the  current- 
strength  by  means  of  the  resistance  board,  a  deposit  of  a  redder 
or  more  pale  yellow  to  greenish  color  can  be  produced.  How- 
ever, with  a  bath  which  does  not  contain  copper  and  zinc  in 
the  correct  proportional  quantities,  and  especially  with  old 
baths  long  in  use,  a  determined  color  of  the  deposit  cannot  be 
produced  with  the  assistance  of  the  resistance  board.  In  such 
case  the  content  of  the  metal  lacking  in  the  bath,  which  is  re- 
quired for  the  production  of  a  determined  color,  must  be  aug- 
mented by  the  addition  of  solution  of  the  respective  metallic 
salt  in  potassium  cyanide. 

Suppose  a  bath  which  originally  contained  copper  and  zinc 
salts  in  equal  proportions  has  been  long  in  daily  use.  Now, 
since  brass  contains  more  copper  than  zinc,  it  is  evident  that 
more  of  the  former  will  be  withdrawn  from  the  bath  than  of  the 
latter,  and  finally  a  limit  will  be  reached  when  the  bath  with  a 
current  suitable  for  the  decomposition  of  the  solution  will  deposit 
a  greenish  or  gray  brass,  and  with  a  weaker  current  produce  no 
deposit  whatever.  The  only  help  in  such  a  case  is  the  addition 
of  sufficient  solution  of  cyanide  of  copper  in  potassium  cyanide, 
so  that,  even  with  quite  a  powerful  current,  a  deposit  of  a 
beautiful  brass  color  is  produced,  the  shades  of  which  can  then 
again  be  controlled  with  the  help  of  the  resistance  board. 
However,  it  must  not  be  forgotten  that  every  addition  of  a 
metallic  salt  momentarily  irritates  the  brass  bath,  making  it,  so 
to  say,  sick,  and  to  confine  this  phenomenon  to  the  narrowest 
limit,  an  addition  of  carbonate  and  bisulphite  of  soda  should  at 
the  same  time  be  made,  and  the  bath  be  worked  through  with 
the  current  as  previously  described,  until  a  test  shows  that  it 
works  in  a  regular  manner. 

Annealed  sheets  of  brass  not  rolled  too  hard,  and  of  as  nearly 
as  possible  the  same  composition  and  color  the  deposit  is  to 
show,  are  used  as  anodes.  The  anode-surface  should  be  at 


DEPOSITION    OF   COPPER,  BRASS,  AND    BRONZE.  245 

least  twice  as  large  as  that  of  the  objects  to  be  brassed,  though 
it  is  best  to  use  as  many  anodes  as  the  anode-rods  will  hold. 

As  in  the  copper  bath,  an  abundant  formation  of  slime  on 
the  anodes  indicates  the  want  of  potassium  cyanide  in  the  bath. 
In  this  case  the  evolution  of  gas  bubbles  on  the  objects  is  very 
slight,  and  the  deposit  forms  slowly.  This  is  remedied  by  an 
addition  of  potassium  cyanide.  The  slow  formation  of  the  de- 
posit, however,  may  also  be  due  to  a  want  of  metallic  salts ;  in 
this  case  not  only  potassium  cyanide,  but  also  solution  of 
cyanide  of  copper  and  cyanide  of  zinc  in  potassium  cyanide, 
has  to  be  added.  For  this  purpose  prepare  a  concentrated 
solution  of  potassium  cyanide  in  water,  and  a  solution  of  equal 
parts  of  blue  vitriol  and  zinc  sulphate  in  water.  From  the 
latter  precipitate  the  copper  and  zinc  as  carbonates  with  a 
solution  of  carbonate  of  soda,  as  given  in  formula  I.,  p.  239. 
After  allowing  the  precipitate  to  settle,  pour  off  the  clear 
supernatant  fluid  and  add  to  the  precipitate,  with  vigorous 
stirring,  of  the  potassium  cyanide  solution,  until  it  is  dissolved ; 
if  heating  takes  place  thereby,  add  from  time  to  time  a  little 
cold  water.  Add  this  solution  with  a  small  excess  of  potassium 
cyanide,  and  the  addition  of  carbonate  or  bisulphite  of  soda,  to 
the  bath,  and  boil  the  latter  or  work  it  through  with  the  current. 
A  more  simple  method  is  to  procure  cyanide  of  copper  and 
cyanide  of  zinc,  or  concentrated  solutions  of  these  combina- 
tions, from  a  dealer  in  such  articles.  In  the  first  case  rub  in  a 
mortar  equal  parts  of  cyanide  of  zinc  and  cyanide  of  copper 
•with  water  to  a  thickly  fluid  paste.  Pour  this  paste  into  potas- 
sium cyanide  solution,  containing  about  7  ozs.  of  potassium 
cyanide  to  the  quart,  as  long  as  the  metallic  cyanides  dissolve 
quite  rapidly  with  stirring.  When  solution  takes  place  but 
slowly,  stop  the  addition  of  paste. 

When  a  brass  bath  contains  too  large  an  excess  of  potassium 
cyanide,  a  very  vigorous  evolution  of  gas  takes  place  on  the 
objects,  but  the  deposit  is  formed  slowly  or  not  at  all ;  besides, 
the  deposit  formed  has  a  tendency  to  peel  off  in  scratch-brush- 
ing. In  this  case  the  injurious  excess  has  to  be  removed,  which 


246  ELECTRO-DEPOSITION    OF    METALS. 

is  effected  by  pouring,  with  vigorous  stirring,  a  quantity  of  the 
above-mentioned  thinly  fluid  paste  of  cyanide  of  zinc  and  of 
copper  into  the  bath. 

To  avoid  unnecessary  repetition  we  refer,  as  regards  the  pro- 
duction of  thick  deposits,  scatch-brushing  and  polishing  of  the 
plated  articles,  to  what  has  been  said  under  "  Execution  of 
Coppering,"  the  directions  given  there  being  also  valid  for 
brassing. 

The  deposition  of  several  metals  from  a  common  solution  is 
not  an  easy  task,  and  requires  attention  and  experience;  if, 
however,  the  directions  given  in  this  chapter  are  followed,  the 
operator  will  be  able  to  conduct,  after  short  experience,  the 
brassing  process  with  the  same  success  as  one  in  which  but  one 
metal  is  deposited. 

In  brassing,  the  distance  of  the  objects  to  be  brassed  from 
the  anodes  is  of  considerable  importance.  If  objects  with  deep 
depressions  or  high  reliefs  are  hung  in  the  brass  bath,  it  will  be 
found  that,  with  the  customary  distance  of  3  ^  to  5  ^  inches 
from  the  anodes,  the  brassing  of  the  portions  in  relief  nearest  to 
the  anodes  will  turn  out  of  a  lighter  color  than  that  of  the  de- 
pressed portions,  which  will  show  a  redder  deposit,  the  reason 
for  this  being  that  the  current  acts  more  strongly  upon  the 
portions  in  relief,  and  consequently  deposits  more  zinc  than  the 
weaker  current,  which  strikes  the  depressions.  To  equalize  the 
difference,  the  objects  have  to  be  correspondingly  further  re- 
moved from  the  anodes,  with  lamp-feet  up  to  9^  inches,  and 
even  more,  when  a  deposit  of  the  same  color  will  be  every- 
where formed. 

The  brassing  of  unground  iron-castings  is  especially  trouble- 
some, and  in  order  to  obtain  a  beautiful  and  clean  deposit  the 
preliminary  scratch-brushing  has  to  be  executed  with  special 
care ;  but  even  then  the  color  of  the  brass  deposit  will  some- 
times be  found  to  possess  a  disagreeable  gray  tone.  This  is 
very  likely  largely  due  to  the  quality  of  the  iron  itself,  and  it  is 
advisable  first  to  give  the  casting  a  thin  coat  of  nickel  or  tin, 
upon  which  a  deposit  of  brass  of  the  usual  brilliancy  can  be 


rr  1 

•  '-" 


DEPOSITION    OF   COPPER,  BRASS,  AND    BRONZE.  247 

produced.  In  baths  serving  for  brassing  iron  articles,  a  large 
excess  of  potassium  cyanide  must  be  avoided  ;  it  is,  however, 
an  advantage  to  increase  the  content  of  carbonate  of  soda. 

Brassing  by  contact  and  dipping. — Some  authors  have  given 
directions  for  brassing  by  contact — for  instance,  Bacco,  Weil, 
and  others — but  the  results  obtained  are  so  unsatisfactory,  and 
the  process  so  uncertain,  that  it  is  not  necessary  to  enter  into 
further  details. 

The  inlaying  with  black  of  brassed  articles  is  done  in  the  same 
manner  as  described  under  "  Coppering." 

For  oxidizing,  platinizing,  and  coloring  of  brass,  see  the 
proper  chapter. 

3.  Bronzing. 

Tbe  electro-plating  of  metallic  objects  with  bronze,  i.  e.,  a 
copper-tin  alloy,  or  an  alloy  of  copper,  tin,  and  zinc,  is  but 
seldom  practised,  the  bronze  tone  being  in  most  cases  imitated 
by  a  deposit  of  brass,  with  a  somewhat  larger  content  of  copper. 

For  coating  wrought-  and  cast-iron  with  bronze,  Gountier  re- 
commends the  following  solution:  — 

Yellow  prussiate  of  potash  10^  ozs.,  cuprous  chloride  5^ 
ozs.,  stannous  chloride  (tin  salt)  14  ozs.,  sodium  hyposulphite 
14  ozs.,  water  TO  quarts. 

According  to  Ruolz,  a  bronze  bath  is  prepared  as  follows: 
Dissolve  at  122°  to  140°  F.,  cyanide  of  copper  2.11  ozs.,  and 
oxide  of  tin  0.7  oz.  in  10  quarts  of  potassium  cyanide  solution 
of  4°  Be.  The  solution  is  to  be  filtered. 

Eisner  prepares  a  bronze  bath  by  dissolving  21  ozs.  of  blue 
vitriol  in  10  quarts  of  water,  and  adding  a  solution  of  2^  ozs. 
of  chloride  of  tin  in  potash  lye. 

Salzede  recommends  the  following  bath,  which  is  to  be  used 
at  between  86°  and  95°  F. :  Potassium  cyanide  3J^  ozs.,  car- 
bonate of  potash  35  J^  ozs.,  stannous  chloride  (tin  salt)  0.42 
oz.,  cuprous  chloride  ^  oz.,  water  10  quarts. 

Weil  and  Newton  claim  to  obtain  beautiful  bronze  deposits 
from  solutions  of  the  double  tartrate  of  copper  and  potash,  and 


248  KLECTRO-DEPOSITION    OF   METALS. 

the  double  tartrate  of  the  protoxide  of  tin  and  potash,  with 
caustic  potash,  but  fail  to  state  the  proportions. 

The  above  formulae  are  here  given  with  all  reserve,  since  ex- 
periments with  them  failed  to  give  satisfactory  results ;  with 
Gountier's,  Ruolz's,  and  Eisner's  baths  no  deposit  was  obtained, 
but  only  a  strong  evolution  of  hydrogen,  while  even  with  a 
strong  current  Salzede's  bath  did  not  yield  a  bronze  deposit, 
but  simply  one  of  tin. 

The  following  method  of  preparing  a  bronze  bath  may  be 
recommended :  Prepare,  each  by  itself,  solutions  of  phosphate  of 
copper  and  stannous  chloride  (tin  salt)  in  sodium  pyrophos- 
phate.  From  a  blue  vitriol  solution  precipitate,  with  sodium 
phosphate,  phosphate  of  copper,  allow  the  latter  to  settle,  and 
after  pouring  off  the  clear  supernatant  fluid  bring  it  to  solution 
by  concentrated  solution  of  sodium  pyrophosphate.  On  the 
other  hand,  add  to  a  saturated  solution  of  sodium  pyrophos- 
phate solution  of  tin  salt  as  long  as  the  milky  precipitate  formed 
dissolves.  Of  these  two  metallic  solutions  add  to  a  solution  of 
sodium  pyrophosphate,  which  contains  about  I  ^  ozs.  of  the 
salt  to  the  quart,  until  the  precipitate  appears  quickly  and  of 
the  desired  color.  For  anodes,  use  cast  bronze  plates,  which 
dissolve  well  in  the  bath.  Some  sodium  phosphate  has  from 
time  to  time  to  be  added  to  the  bath,  and  if  the  color  becomes 
too  light,  solution  of  copper,  and  if  too  dark,  solution  of  tin. 

For  deposits  of  tombac  Hess's  bath  (formula  VIL,  brassing) 
with  anodes  of  plate  or  sheet  tombac  can  be  recommended ;  3 
to  3.5  volts  being  the  most  suitable  tension  of  the  current  for 
the  decomposition  of  the  bath. 

For  nickel  bronze,  see  p.  220. 

The  execution  of  bronzing  requires  the  same  attention  and 
manipulations  as  given  for  brassing. 


DEPOSITION    OF    SILVER.  249 

CHAPTER  IX. 

DEPOSITION  OF  SILVER. 

Properties  of  silver. — Pure  silver  is  the  whitest  of  all  known 
metals;  it  takes  a  fine  polish,  is  softer  and  less  tenacious  than 
copper,  but  harder  and  more  tenacious  than  gold.  It  is  very 
malleable  and  ductile,  and  can  be  obtained  in  exceedingly  thin 
leaves  and  fine  wire.  Its  specific  gravity  is  10.48  to  10.5,  ac- 
cording to  whether  it  is  cast  or  hammered.  It  melts  at  about 
1832°  F.  It  is  unacted  upon  by  the  air,  but  in  the  atmosphere 
of  towns  it  gradually  becomes  coated  with  a  film  of  silver  sul- 
phide. It  is  rapidly  dissolved  by  nitric  acid,  nitrogen  dioxide 
being  evolved ;  hydrochloric  acid  has  but  little  action  upon  it 
even  at  boiling  heat ;  when  heated  with  concentrated  sulphuric 
acid  it  yields  sulphur  dioxide  and  silver  sulphate. 

Silver  baths. — Only  formulae  for  approved  baths  will  be  given. 

Silver  bath  for  a  heavy  electro-deposit  of  silver  (silvering  by 
weight). — I.  98  per  cent,  potassium  cyanide  14  ozs.,  fine  silver 
as  silver  chloride  8^  ozs.,  distilled  water  10  quarts. 

\a.  98  per  cent,  potassium  cyanide  8^  ozs.,  fine  silver  as 
silver  cyanide  8^  ozs.,  distilled  water  10  quarts. 

Before  describing  the  preparation  of  the  bath  a  few  words  may 
be  said  in  regard  to  the  old  dispute  whether  it  is  preferable  to 
use  silver  cyanide  or  silver  chloride.  Without  touching  upon 
all  the  arguments  advanced,  it  may  be  asserted  by  reason  of 
conscientious  comparative  experiments  that  the  results  are  the 
same  and  that  the  life  of  the  bath  is  also  the  same  whether  one 
or  the  other  salt  has  been  used  in  the  original  preparation. 
From  a  theoretical  standpoint,  silver  cyanide  must  be  given  the 
preference ;  but  as  the  disadvantages  in  respect  to  the  life  of 
the  bath  ascribed  by  some  to  silver  chloride  do  not  exist,  it 
might  be  advisable  for  tho?e  who  prepare  their  own  baths  to 
use  silver  chloride. 

Preparation  of  bath  I.  with  silver  chloride.— Dissolve  14  ozs. 


250  ELECTRO-DEPOSITION    OF    METALS. 

of  chemically  pure  nitrate  of  silver,  best  the  crystallized  and  not 
the  fused  article,  in  5  quarts  of  water,  and  add  to  the  solution 
pure  hydrochloric  acid  or  common  salt  solution,  with  vigorous 
stirring  or  shaking,  until  a  sample  of  the  fluid  filtered  through 
a  paper  filter  forms  no  longer  a  white  caseous  precipitate  of 
silver  chloride  when  compounded  with  a  drop  of  hydrochloric 
acid.  These,  as  well  as  the  succeeding  operations  until  the 
silver  chloride  is  complete,  have  to  be  performed  in  a  darkened 
room,  as  silver  chloride  is  partially  decomposed  by  light.  Now 
separate  the  precipitate  of  silver  chloride  from  the  solution  by 
filtering,  using  best  a  large  bag  of  close  felt,  and  wash  the  pre- 
cipitate in  the  felt  bag  with  fresh  water.  Continue  the  washing 
until  blue  litmus-paper  is  no  longer  reddened  by  the  wash- 
water,  if  the  hydrochloric  acid  was  used  for  precipitating,  or,  if 
common  salt  solution  was  used,  until  a  small  quantity  of  the 
wash-water  on  being  mixed  with  a  drop  of  lunar  caustic  solu- 
tion produces  oaly  a  slight  milky  turbidity  and  no  precipitate. 
Now  bring  the  washed  silver  chloride  in  portions  from  the  felt 
bag  into  a  porcelain  mortar,  rub  it  with  water  to  a  thin  paste, 
and  pour  the  latter  into  the  potassium  cyanide  solution  consist- 
ing of  I4ozs.  of  98  per  cent,  potassium  cyanide  in  5  quarts  of 
water,  in  which,  with  vigorous  stirring,  the  silver  chloride  gradu- 
ally dissolves.  All  the  precipitated  silver  chloride  having  been 
brought  into  solution,  dilute  with  water  to  10  quarts  of  fluid  and 
boil  the  bath,  if  possible,  for  one  hour,  replacing  the  water  lost 
by  evaporation.  A  small  quantity  of  black  sediment  contain- 
ing silver  thereby  separates,  from  which  the  colorless  fluid  is 
filtered  off.  The  sediment  is  added  to  the  silver  residues  and  is 
worked  together  with  them  for  the  recovery  of  the  silver  by  one 
of  the  methods  to  be  described  later  on. 

Preparation  of  bath  la.  with  silver  cyanide. — Dissolve  14 
ounces  of  chemically  pure  crystallized  nitrate  of  silver  in  5 
quarts  of  water,  and  precipitate  the  silver  with  prussic  acid, 
adding  the  latter  until  no  more  precipitate  is  produced  by  the 
addition  of  a  few  drops  of  prussic  acid  to  a  filtered  sample  of 
the  fluid.  Now  filter,  wash  out,  and  proceed  for  the  rest  exactly 


DEPOSITION    OF    SILVER.  251 


as  stated  for  the  bath  with  silver  chloride,  except  that  only 
ounces  of  potassium  cyanide  are  taken  for  dissolving  the  silver 
cyanide.  In  working  with  prussic  acid  avoid  inhaling  the  vapor 
which  escapes  from  the  liquid  prussic  acid,  especially  in  the 
warm  season  of  the  year  ;  and  be  careful  the  acid  does  not  come 
in  contact  with  cuts  on  the  hands.  It  is  one  of  the  most  rapidly 
acting  poisons. 

Cyanide  of  silver  may  also  be  prepared  as  follows  :  Dissolve 
14  ounces  of  chemically  pure  crystallized  nitrate  of  silver  in  5 
quarts  of  water,  and  add  moderately  concentrated  potassium 
cyanide  solution  until  no  more  precipitate  is  formed,  avoiding, 
however,  an  excess  of  the  precipitating  agent,  as  it  would  again 
dissolve  a  portion  of  the  cyanide  of  silver.  The  precipitated 
cyanide  of  silver  is  filtered  off,  washed  and  dissolved  in  potas- 
sium cyanide,  as  above  described. 

The  bath  prepared  according  to  formula  I.  or  la.,  serves 
chiefly  for  thickly  silvering  objects  of  German  silver  ;  it  may, 
however,  be  used  for  silvering  other  metals  by  weight. 

Silver  bath  for  ordinary  electro-  silvering.  —  II,  98  per  cent. 
potassium  cyanide  6)^  to  7  ounces,  fine  silver  (as  silver  nitrate 
or  chloride),  3^  ounces;  distilled  water,  10  quarts. 

To  prepare  the  bath  dissolve  5J^  ounces  of  chemically  pure 
crystallized  nitrate  of  silver  in  5  quarts  of  distilled  water;  in  the 
other  5  quarts  of  water  dissolve  the  potassium  cyanide,  and  mix 
both  solutions.  Or,  if  chloride  of  silver  is  to  be  used,  precipi- 
tate the  solution  of  3  J^  ounces  of  the  silver  salt  in  the  same 
manner  as  given  for  formula  I.  ;  wash  the  precipitated  chloride 
of  silver,  and  dissolve  it  in  the  potassium  cyanide  solution. 

Vats  of  stoneware,  enameled  iron,  or  lined  with  ebonite  mass 
are  to  be  used  for  the  silver  baths. 

Treatment  of  the  silver  baths  ;  the  silver  anodes.  Frequently 
the  error  is  committed  of  adding  too  much  potassium  cyanide 
to  the  bath.  A  certain  excess  of  it  must  be  present,  and,  in 
the  formulae  given,  this  has  been  taken  into  consideration.  For 
dissolving  the  cyanide  of  silver  prepared  from  14  ounces  of 
nitrate  of  silver,  as  given  in  formula  la,  only  about  5J^  ounces 


252  ELECTRO-DEPOSITION    OF   METALS. 

of  potassium  cyanide  are  required,  and  the  consequence  of  work- 
ing with  such  a  bath  devoid  of  all  excess  would  be  that,  on  the 
one  hand,  the  bath  would  offer  considerable  resistance  to  the 
current,  and,  on  the  other,  that  the  deposit  would  not  be  uni- 
form and  homogeneous.  Hence  with  the  use  of  a  medium 
strong  current  about  30  to  35  per  cent,  more  potassium  cyanide 
than  fine  silver  fs  taken.  In  working  with  a  stronger  current, 
this  excess  would,  however,  be  too  large,  in  consequence  of 
which  the  deposit  would  not  adhere  properly  and  would  peel 
off  in  scratch-brushing.  And  again,  with  a  weak  current  the 
baths  can,  without  disadvantage,  stand  a  larger  excess.  As  a 
rule,  however,  the  proportion  between  fine  silver  and  potassium 
cyanide  in  the  above  formula  may  be  considered  as  normal,  and 
the  current-strength  will  have  to  be  regulated  so  that  a  deposit 
of  fine  structure,  which  adheres  firmly,  is  formed.  The  most 
suitable  current-strength  per  1^/4  square  inches  of  surface  is 
0.25  to  0.15  ampere,  and  0.5  to  0.75  volt  tension;  the  tension 
of  a  Daniell  element  being  more  than  sufficient  for  the  decom- 
position of  the  silver  bath.  On  account  of  the  silver  bath  re- 
quiring a  current  of  slight  electro-motive  force,  the  Smee  ele- 
ment, which  yields  0.48  volt,  is  much  liked  for  silvering  in  this 
country  and  in  England.  The  Bunsen  element  may,  however, 
also  be  used  if  the  surface  to  be  silvered  is  made  to  correspond 
with  the  energy  of  such  an  element ;  or  if  a  resistance  board  is 
placed  in  the  circuit,  which  is  advisable  in  all  cases.  On  ac- 
count of  the  slight  electro-motive  force  required  in  silvering 
larger  surfaces  of  objects,  the  elements  are  not  to  be  coupled 
one  after  the  other  for  electro-motive  force,  but  alongside  one 
another  for  quantity.  In  no  case  must  an  evolution  of  hydro- 
gen be  perceptible  on  the  articles,  and  the  current  must  be 
more  weakened  the  larger  the  excess  of  potossium  cyanide  in 
the  bath. 

Whether  too  much,  or  not  enough,  potassium  cyanide  is 
present  in  the  bath  is  indicated  by  the  appearance  of  the  silvered 
objects  and  the  properties  of  the  deposit,  as  well  as  by  the  be- 
havior of  the  anodes  in  the  bath  during  and  after  silvering. 


DEPOSITION    OF    SILVER.  253 

It  may  be  accepted,  as  a  rule,  that  with  a  moderate  current 
the  object  must,  in  the  course  of  10  to  15  minutes,  be  coated 
with  a  thin,  dull  white  film  of  silver.  If  this  be  not  the  case  and 
the  film  of  silver  shows  a  meagre  bluish-white  tone,  potassium 
cyanide  is  wanting.  However,  if,  on  the  other  hand,  the  dull 
white  deposit  forms  within  2  to  3  minutes,  and  shows  a  crystal- 
line structure,  or  a  dark  tone  playing  into  gray- black,  the  con- 
tent of  potassium  cyanide  in  the  bath  is  too  large,  provided  the 
current  is  not  excessively  strong.  If  copper  and  brass  become 
coated  with  silver  without  the  assistance  of  the  current,  the  bath 
contains  also  too  much  potassium  cyanide. 

In  silvering,  even  if  the  objects  are  to  be  but  thinly  coated, 
insoluble  platinum  anodes  should  never  be  used,  but  only 
anodes  of  fine  silver,  which  are  capable  of  keeping  the  content 
of  silver  in  the  bath  quite  constant.  From  the  behavior  and 
appearance  of  the  anodes,  a  conclusion  may  also  be  drawn  as 
to  whether  the  content  of  potassium  cyanide  in  the  bath  is  too 
large  or  too  small.  If  the  anodes  remain  silver-white  during 
silvering,  it  is  a  sure  sign  that  the  bath  contains  more  potas- 
sium cyanide  than  is  necessary  and  desirable ;  but  if  they  turn 
gray  or  blackish,  and  retain  this  color  after  silvering  when  no 
current  is  introduced  into  the  bath  for  a  quarter  of  an  hour  or 
more,  potassium  cyanide  is  wanting.  On  the  other  hand,  the 
correct  content  of  potassium  cyanide  is  present  when  the 
anodes  acquire  during  the  silvering  process  a  gray  tone,  which, 
after  the  interruption  of  the  current,  gradually  changes  back  to 
a  pure  white. 

The  proposition  to  use  steel  plates  in  place  of  silver  anodes 
cannot  be  approved,  and  as  regards  such  anodes  the  reader  is 
referred  to  what  is  said  under  "  Gilding." 

If  it  is  shown  by  the  process  of  silvering  itself  or  by  the  ap- 
pearance of  the  articles  or  of  the  anodes  that  potassium  cyanide 
is  wanting  in  the  bath,  it  should  be  quickly  added,  though  never 
more  than  30  to  37^  grains  per  quart  of  bath  at  one  time,  so 
as  to  avoid  going  to  the  other  extreme.  Too  large  a  content 
of  potassium  cyanide  is  remedied  by  adding  to  the  bath,  with 


254  ELECTRO-DEPOSITION    OF   METALS. 

constant  stirring,  a  small  quantity  of  cyanide  or  chloride  of 
silver  rubbed  with  water  to  a  thinly-fluid  paste,  whereby  the 
excess  is  rendered  harmless  in  consequence  of  the  formation  of 
the  double  salt  of  silver  and  potassium  cyanide.  Instead  of 
such  addition,  the  current  may,  however,  be  used  as  a  corrector 
of  the  excess.  For  this  purpose  suspend  as  many  silver  anodes 
as  possible  to  the  anode-rods,  but  only  a  single  anode  as  an 
object  to  the  object  rod,  and  allow  the  current  to  pass  for  a  few 
hours  through  the  bath,  whereby  the  excess  of  potassium 
is  cyanide  rendered  innoxious  by  the  dissolving  silver. 

The  bath  can  be  kept  quite  constant  by  silver  anodes,  pro- 
vided potassium  cyanide  be  regularly  added  at  certain  intervals, 
and  the  anode-surface  is  equal  to  that  of  the  objects  to  be  sil- 
vered. But  since,  on  account  of  the  expense,  a  relatively  small 
anode  surface  is  frequently  used,  the  content  of  silver  in  a  bath 
continuously  worked  will  finally  become  lower,  and  augmenta- 
tion, by  the  addition  of  silver,  will  be  required.  The  manner 
of  effecting  this  augmentation  depends  on  whether  the  baths 
are  used  for  silvering  by  weight  or  for  lighter  silvering,  or 
whether  the  baths  are  worked  without  stopping  from  morning 
till  evening.  If  the  content  of  silver  in  baths  I.  and  la.  is  not 
to  be  augmented  by  the  current  itself,  it  is  best  to  use  ex- 
clusively solution  of  silver  cyanide  in  potassium  cyanide.  If, 
however,  the  working  of  such  a  bath  can  for  some  time  be  in- 
terrupted, then  add  not  too  small  a  quantity  of  potassium 
cyanide  to  the  bath,  and,  after  hanging  a  small  silver  anode  on 
the  object-rod  and  a  sufficient  number  of  anodes  on  the  anode- 
rods,  dissolve  with  not  too  weak  a  current  silver  from  the  anodes 
until  the  latter,  which  at  first  remain  white,  begin  to  acquire  a 
gray  tone.  Silver  is,  of  course,  deposited  upon  the  anode  sus- 
pended as  an  object,  which  is,  however,  not  lost,  it  being  dis- 
solved later  on  when  the  anode  is  secured  to  the  anode-rod. 
The  quantity  .of  silver  dissolved  is  considerably  larger  than  that 
deposited  upon  the  small  anode-surface  suspended  as  an  object. 
It  has  previously  been  mentioned  that  with  proper  treatment 
baths  made  with  chloride  of  silver  have  the  same  duration  of  life 


DEPOSITION    OF    SILVER.  255 

as  those  prepared  with  cyanide  of  silver.  The  chief  feature  of 
such  proper  treatment  is  the  augmentation  of  the  content  of 
silver  by  electrolysis,  i.  e.,  by  the  current  itself.  If  it  were  not 
possible  to  proceed  in  this  manner,  the  bath,  by  the  frequently 
repeated  additions  of  solution  of  the  chloride,  instead  of  the 
cyanide  of  silver,  in  potassium  cyanide,  would  gradually  thicken 
by  reason  of  the  potassium  chloride  which  is  thereby  simul- 
taneously introduced,  and  in  consequence  of  this  would  offer 
greater  resistance  to  the  current.  The  fear  expressed  by  some 
that  a  crystalline  separation  of  potassium  chloride,  and  the 
consequent  formation  of  a  porous  deposit  upon  the  objects, 
might  take  place,  is  erroneous,  potassium  chloride  being  one  of 
the  most  soluble  salts  and  showing  but  little  tendency  to  sepa- 
rate in  crystals  from  aqueous  solutions.  The  above-mentioned 
gradual  thickening  is,  however,  a  disadvantage,  which  shows 
itself  by  the  deposit  being  less  homogeneous,  and  for  this 
reason  it  is  advisable,  when  silvering  by  weight,  to  use  silver 
cyanide  instead  of  the  chloride  for  strengthening  the  silver  bath. 

A  gradual  thickening  of  the  bath  may  also  take  place  if  potas- 
sium cyanide  containing  potash  is  used  instead  of  the  prepara- 
tion free  from  potash,  and  of  98  to  99  per  cent,  purity.  Even 
pure  fused  potassium  cyanide  produces  a  thickening  of  the 
bath,  which,  however,  progresses  very  slowly.  This  thickening 
is  due  to  a  portion  of  the  excess  of  potassium  cyanide  being 
converted  by  the  action  of  the  air  into  potassium  carbonate. 
The  latter  thus  formed  must  from  time  to  time  be  neutralized, 
which  is  mostly  done  with  prussic  acid,  the  potassium  carbon- 
ate being  thereby  converted  into  potassium  cyanide.  Instead 
of  prussic  acid,  calcium  cyanide  or  barium  cyanide  may  be 
added  as  long  as  a  precipitate  of  calcium  carbonate  or  barium 
carbonate  is  formed,  the  clear  solution  being  separated  from 
the  precipitate  by  filtering. 

For  augmenting  the  content  of  silver  in  baths  prepared  ac- 
cording to  formula  II.,  solution  of  nitrate  of  silver  or  of  chloride 
of  silver  in  potassium  cyanide  may  unhesitatingly  be  used,  since 
the  thickening  proceeds  more  slowly  on  account  of  the  smaller 


I 

256  ELECTRO-DEPOSITION   OF   METALS. 

content  of  salt  in  the  bath,  and  because  a  cheaper  bath  can  be 
more  readily  renewed  without  the  sacrifice  of  money  than  one  for 
heavy  silvering.  The  recovery  of  silver  from  old  baths  is  ef- 
fected by  one  of  the  methods  given  later  on. 

To  determine  whether  the  bath  contains  silver  and  excess  of 
potassium  cyanide  in  proper  proportions,  the  following  method 
may  be  used:  Dissolve  I  gramme  (15.43  grains)  of  chemically 
pure  crystallized  nitrate  of  silver  in  20  grammes  (0.7  oz.)  of 
water,  and  gradually  add  this  solution,  with  constant  stirring 
with  a  glass  rod,  to  100  grammes  (3.52  ozs.)  of  the  silver  bath 
in  a  beaker  glass  as  long  as  the  precipitate  of  silver  cyanide 
formed  dissolves  by  itself.  If,  after  adding  the  entire  quantity 
of  silver  solution,  the  precipitate  dissolves  rapidly,  too  large  an 
excess  of  potassium  cyanide  is  present  in  the  bath  ;  and  vice 
versa,  if  the  precipitate'  does  not  completely  dissolve  after 
stirring,  potassium  cyanide  is  wanting. 

While  this  experiment  allows  us  to  judge  of  the  proportion 
of  silver  to  potassium  cyanide,  it  does  not  throw  any  light  upon 
the  effective  content  of  silver  in  the  bath,  and  for  refreshing 
the  latter,  it  is  desirable  to  know  the  actual  content  of  silver  in  it 
To  determine  this,  mix  25  cubic  centimetres  of  the  silver  bath 
in  a  beaker  glass  with  50  cubic  centimetres  of  pure  hydro- 
chloric acid  and  50  cubic  centimetres  of  water,  and  heat  upon 
a  water  or  sand  bath  until  all  odor  of  prussic  acid  has  disap- 
peared, and  then  dilute  with  200  cubic  centimetres  of  water. 
Filter  off  the  precipitate  of  chloride  of  silver  formed  through  a 
weighed  filter,  previously  dried  at  212°  F.,  wash  the  precipitate 
with  hot  distilled  water  until  the  filtrate  is  no  longer  rendered 
turbid  by  a  drop  of  silver  solution  ( I  part  of  nitrate  of  silver  to 
20  of  water),  and  dry  at  212°  F.  until  the  weight  remains  con- 
stant. After  deducting  the  weight  of  the  dried  filter,  the  weight 
of  the  precipitated  chloride  of  silver  is  obtained,  and  from  this 
the  weight  of  the  metallic  silver  is  calculated  according  to  the 
following  formula: — 

143.5  :  IQ8  =  grammes  of  chloride  of  silver  found :  x. 


DEPOSITION   OF   SILVER. 


257 


The  content  of  silver  in  the  bath  per  liter  is  then  found  by 
multiplying  x  by  40. 

In  silvering,  the  constant  agitation  of  the  layers  of  fluid  is  of 
decided  advantage,  streaks  being  otherwise  readily  formed  upon 
the  silvered  objects.  To  keep  the  articles  in  gentle  motion  while 
in  the  bath,  one  method  is  to  connect  the  suspending  rods  to  a 
frame  of  iron  having  four  wheels,  about  3  inches  in  diameter, 
connected  to  it,  which  slowly  travel  to  and  fro  to  the  extent  of 
3  or  4  inches  upon  inclined  rails  attached  to  the  upper  edges  of 
the  tank,  the  motion,  which  is  both  horizontal  and  vertical,  be- 
ing given  by  means  of  an  eccentric  wheel  driven  by  steam 

FIG.  115. 


power.  By  another  arrangement,  the  frame  supporting  the 
articles  does  not  rest  upon  the  tank,  but  is  suspended  above 
the  bath,  and  receives  a  slow  swinging  motion  from  a  small 
eccentric  or  its  equivalent.  In  the  Elkington  establishment  at 
Birmingham  the  following  arrangement  is  in  use :  All  the  sus- 
pending rods  of  the  bath  rest  upon  a  copper  mounting,  which, 
by  each  revolution  of  an  eccentric  wheel,  is  lifted  about  ^ 
inch,  and  then  returned  to  its  position ;  the  copper  mounting 
is  connected  to  the  main  negative  wire  of  the  dynamo-machine 
by  a  copper  cable.  The  same  object  may  also  be  attained  by 


258  ELECTRO-DEPOSITION    OF   METALS. 

giving  the  objects  at  horizontal  instead  of  vertical  motion,  as 
shown  in  Fig.  115,  in  which  the  motion  is  produced  by  an  ec- 
centric wheel  on  the  side. 

Finally  it  remains  to  mention  a  singular  phenomenon  in 
silvering  which  has  not  yet  been  explained.  A  small  addition 
of  certain,  and  especially  of  organic,  substances,  which,  how- 
ever, must  not  be  made  suddenly  or  in  too  large  quantities,  pro- 
duces a  fuller  and  better  adhering  deposit  of  greater  lustre  than 
can  be  produced  in  fresh  baths.  Elkington  observed  that  an 
addition  of  a  few  drops  of  carbon  disulphide  to. the  bath  made 
the  silvering  more  lustrous,  while  others  claim  to  have  used 
with  success  solutions  of  iodine  in  chloroform,  of  gutta-percha 
in  chloroform,  as  well  as  heavy  hydrocarbons,  tar,  oils,  etc. 
However,  many  baths  have  been  entirely  spoiled  by  an  attempt 
to  change  them  into  bright  working  baths  by  the  addition  of 
such  ingredients ;  and  hence  it  is  best  to  leave  such  experi- 
ments alone.  There  is  no  doubt  that  a  silver  bath  becomes 
better  in  the  degree  as  it  takes  up  small  quantities  of  organic 
substances  from  dust  and  air.  Fresh  silver  baths  will  more 
rapidly  accommodate  themselves  to  regular  working  by  the  x 
addition  of  a  few  drops  of  spirit  of  sal  ammoniac. 

After  silvering  the  objects  frequently  show,  instead  of  a  pure 
white,  a  yellow  tone,  or  they  become  yellow  in  the  air,  which  is 
ascribed  to  the  formation  of  basic  silver  salts  in  the  deposit.  To 
overcome  this  evil  it  has  been  proposed  to  allow  the  objects  to 
remain  in  the  bath  for  a  few  minutes  after  interrupting  the  cur- 
rent, whereby  the  basic  salts  are  dissolved  by  the  potassium 
cyanide  of  the  bath ;  or  the  same  object  is  attained  by  invert- 
ing the  electrodes  for  a  few  seconds,  after  plating,  thus  trans- 
forming the  articles  into  anodes.  The  electric  current  carries 
away  the  basic  salt  of  silver  in  preference  to  the  metal.  This 
operation  should,  of  course,  not  be  prolonged,  otherwise  the 
silver  will  be  entirely  removed  from  the  objects,  and  will  be  de- 
posited on  the  anodes.  For  the  same  purpose  some  electro- 
platers  hold  in  readiness  a  warrn  solution  of  potassium  cyanide, 
in  which  they  immerse  the  silvered  articles  for  half  a  minute. 


DEPOSITION    OF    SILVER.  259 

It  has  been  proposed  to  add  to  the  silver  baths  a  solution  of 
nickelous  cyanide  in  potassium  cyanide  in  order  to  obtain  a 
deposit  of  a  silver-nickel  alloy  which  is  claimed  to  be  dis- 
tinguished by  its  greater  hardness  and  the  property  of  not  turn- 
ing so  readily  dark.  Numerous  experiments  with  solutions  of 
cyanide  of  silver  and  nickelous  cyanide  in  potassium  cyanide  in 
all  possible  proportions,  and  under  various  tensions  of  current 
and  subsequent  analysis  of  the  deposits  obtained,  showed,  how- 
ever, only  inconsiderable  traces  of  nickel  in  the  silver  deposit, 
which  had  but  a  very  slight  influence  upon  the  hardness  and 
durability  of  the  silver. 

The  London  Metallurgical  Co.  endeavors  to  attain  greater 
hardness  and  power  of  resistance  of  the  silver  by  adding  zinc 
cyanide  or  cadmium  cyanide,  and  has  given  to  this  process  the 
name  of  areas  silvering.  According  to  the  patent  an  addition 
of  20  to  30  per  cent,  of  zinc  or  cadmium  to  the  silver  prevents 
the  tarnishing  of  the  plating,  and  besides  the  deposit  is  claimed 
to  be  lustrous  and  hard.  For  areas  silvering  the  appropriate 
quantity  of  zinc  or  cadmium  or  a  mixture  of  both  metals  is  con- 
verted into  potassium-zinc  cyanide  or  potassium-cadmium  cyan- 
ide, and  this  solution  is  mixed  with  a  corresponding  quantity 
of  solution  of  potassium  silver  cyanide,  with  a  small  excess  of 
potassium  cyanide.  Sheets  of  a  silver-zinc  or  a  silver-cadmium 
_^alloy  are  used  as  anodes. 

Some  English  electro-platers  claim  that  for  many  articles, 
especially  bicycles,  areas  silvering  may  be  substituted  for  nickel- 
ing. 

The  following  experiments  may  serve  as  an  illustration  re- 
garding the  value  of  this  process  as  a  substitute  for  silver-plating 
instruments  and  articles  of  luxury: — 

A  bath  was  prepared  which  contained  per  quart  231^  troy 
grains  of  fine  silver  and  77  troy  grains  cadmium  in  the  form  of 
cyanide  double  salts  with  a  small  excess  of  potassium  cyanide. 
The  most  suitable  tension  of  current  for  the  decomposition  of 
a  pure  potassium-cadmium  cyanide  solution  which  contained 
per  quart  154  troy  grains  of  cadmium  with  the  same  excess  of 


260  ELECTRO-DEPOSITION    OF   METALS. 

potassium  cyanide  as  the  above-mentioned  mixture,  was  found 
to  be  2  volts. 

In  electrolyzing  the  cadmium-silver  bath  at  0.75  volt,  a  uni- 
form silver-white  deposit  similar  to  that  of  pure  silver  was  at 
first  formed.  However,  after  two  hours  the  deeper  places  of 
the  objects  suspended  in  the  bath  showed  crystalline  ex- 
crescences which  felt  sandy  and  could  be  rubbed  off  with  the 
fingers.  After  scratch-brushing  the  articles  and  again  suspend- 
ing them  in  the  bath,  these  sandy  non-adhering  metallic  deposits 
were  rapidly  reformed.  An  analysis  of  the  deposit  separated 
from  the  articles  showed  96.4  per  cent,  silver  and  3.2  per  cent, 
cadmium.  This  deposit  could  without  difficulty  be  polished 
with  the  steel  like  a  pure  silver  deposit,  and  hence  its  hardness 
would  not  seem  greater  than  that  of  pure  silver.  Its  capability 
of  resisting  hydrogen  sulphide  as  compared  with  that  of  pure 
silver  was  scarcely  greater. 

In  another  experiment  electrolysis  was  effected  with  1.25 
volts.  The  deposit  showed  from  the  start  a  coarser  structure, 
and  the  formation  of  the  sandy  non-adhering  deposit  took  place 
much  more  rapidly.  But,  on  the  other  hand,  the  hardness  of 
the  separated  coherent  metal  was  greater  than  that  of  pure 
silver,  and  also  its  power  of  resisting  hydrogen  sulphide.  An 
analysis  of  the  deposit  showed  92.1  per  cent,  silver  and  7.8  per 
cent,  cadmium.  In  both  cases  the  deposit  was  dull  like  that  of 
pure  silver. 

With  a  greater  tension  of  current  the  quantity  of  cadmium  in 
the  deposit  increased  and  the  hardness  of  the  latter  became 
correspondingly  greater.  However,  these  deposits  could  not  be 
considered  serviceable  for  the  above-mentioned  purpose,  because 
they  could  not  be  made  of  sufficient  thickness  as  required  for 
solid  silver-plating  of  forks  and  spoons. 

Execution  of  silvering. — A.  Silvering  by  weight. — Copper, 
brass,  and  all  other  copper  alloys  may  be  directly  silvered  after 
amalgamating  (quicking),  whilst  iron,  steel,  nickel,  zinc,  tin, 
lead,  and  Britannia  are  first  coppered  or  brassed,  and  then 
amalgamated. 


DEPOSITION   OF   SILVER.  26 1 

The  mechanical  and  chemical  preparation  of  the  objects  for 
the  silvering  process  is  the  same  as  described  on  pages  150  and 
156.  To  obtain  well-adhering  deposits  great  care  must  be  ex- 
ercised in  freeing  the  objects  from  grease  and  in  pickling.  As 
a  rule,  objects  to  be  silvered  are  ground  and  polished ;  but 
polishing  must  not  be  carried  too  far,  since  the  deposit  of  silver 
does  not  adhere  well  to  highly  polished  surfaces;  and  in  case 
such  highly-polished  objects  are  to  be  silvered  it  is  best  to 
deprive  them  of  their  smoothness  by  rubbing  with  pumice 
powder,  emery,  etc.,  or  by  pickling. 

The  treatment  of  copper  and  its  alloys,  German  silver  and 
brass,  which  have  chiefly  to  be  considered  in  silvering  by  weight, 
is,  therefore,  as  follows:  — 

1 .  Freeing  from  grease  by  hot  potash  or  soda  lye  ( I  part  of 
caustic  alkali   to  8  or  10  parts  of  water),  or  by  brushing  with 
the  lime-paste  mentioned  on  page  157. 

2.  Pickling  in  a  mixture  of   I  part,  by  weight,  of  sulphuric 
acid  of  66°  Be.  and  10  of  water.     This  pickling  is  only  required 
for  rough  surfaces  of    castings,    ground  articles  being  imme- 
diately after  freeing  from  grease  treated  according  to  3. 

3.  Rubbing  with  a  piece   of   cloth   dipped  in    fine    pumice 
powder  or  emery,  after  which  the  powder  is  to  be  removed  by 
washing. 

4.  Pickling  in  the  preliminary  pickle,  rinsing  in  hot  water, 
and  quickly  drawing  through  the  bright  dipping  bath  (page 
152),  and  again  thoroughly  rinsing  in  several  waters. 

5.  Amalgamating  (quicking}   by  immersion  in  a  solution  of 
mercury,  called  the  quicking  solution,  and  consisting  of  a  solu- 
tion of  0.35  ounce  of  nitrate  of  mercury  in  I  quart  of  water,  to 
which,  with  constant  stirring,  pure  nitric  acid  in  small  portions 
is  added  until  a  clear  fluid   results ;   a  weak  solution  of  potas- 
sium-mercury   cyanide    in    water    is,    however,   preferable    for 
quicking. 

6.  In   the  quicking  solution   the   objects    remain    only    long 
enough  to  acquire  a  uniform    white    coating,  when    they  are 
rinsed  in  clean  water,  and  gone  over  with  a  brush  in  case  the 
quicking  shows  a  gray  instead  of  a  white  tone. 


262  ELECTRO-DEPOSITION   OF   METALS. 

The  objects  are  now  brought  into  the  silver  bath  and  secured 
to  the  suspension  rods  by  slinging-wires  of  copper.     For  forks 
and  spoons  these  wires  are  bent  on  their  extremities 
FIG.  116.      jn  suc]1  a  manner  that  the  fork  or  spoon  may  readily 
be^inserted  or  removed.     Fig.  116  presents  this  ter- 
minal hook.     The  straight   portion   of  these  wires 
which  dips  into  the  liquid  is   covered  with  a  small 
tube  of  India  rubber  or  coated  with  ebonite  mass, 
which  prevents  the  useless  deposit  of  silver  upon  it. 
The  hooped  portions,  however,  become  coated  with 
silver,  which  may  be  removed  by   the  use  of  acids 
after  having  raised  the  India-rubber  tube. 
Introduce  into  the  bath   at  first  a  somewhat  more  powerful 
current,  so  that  the   first    deposit  of    silver  takes  place  quite 
rapidly,  and  after  3  minutes  regulate  the  current  so  that  in  10 
to  15  minutes   the  objects  are   coated  with  a  thin,  dull  film  of 
silver.     At  this  stage  take  them  from  the  bath,  and  after  seeing 
that  all  portions  are  uniformly  coated  with  silver,  scratch-brush 
them  with  a  brass  brush,  which  should,  however,  not  be  too 
fine.     In  doing  this  the  deposit  must  not  raise  up ;   if  at  this 
stage  the  objects   stand  thorough  scratch-brushing,  raising   of 
the  deposit  in  burnishing  later  on  need  not  be  feared. 

Any  places  which  show  no  deposit  of  silver  are  vigorously 
scratch-brushed  with  the  use  of  pulverized  tartar,  then  again 
carefully  cleansed  by  brushing  with  lime-paste  to  remove  any 
impurities  due  to  touching  with  the  hands,  pickled  by  dipping 
in  potassium-cyanide  solution,  rinsed  off  again,  quicked,  and 
after  careful  rinsing  returned  to  the  bath.  Special  care  must 
be  had  not  to  contaminate  the  bath  with  quicking  solution,  as 
this  would  soon  spoil  it. 

The  objects  now  remain  in  the  bath  until  the  deposit  has  ac- 
quired a  weight  corresponding  to  the  desired  thickness.  Knives, 
forks,  and  spoons  receive  a  deposit  of  2.1 1  to  3.52  ozs.  of  silver 
per  dozen,  such  deposit  being  produced  with  elements  in  10  to 
14  hours,  and  with  a  dynamo-electrical  machine  in  4  to  5  hours. 
According  to  Dr.  William  H.  Wahl,  the  amount  of  silver  de- 


* 
DEPOSITION    OF    SILVER.  263 

posited  upon  the  several  grades  of  plated  table-ware  manu- 
factured by  the  William  Rogers  Manufacturing  Co.,  of  Hartford, 
Conn.,  is  as  follows:  — 

Per  gross.  Extra  plate.  Double  plate.  Triple  plate. 

Teaspoons 48  dwts.  4  ozs.  6  ozs. 

Desertspoons  and  forks   . . . . 72      "  6   "  9    " 

Tablespoons  and  med.  forks. 96     "  8    "  12    " 

In  order  to  control  the  weight  of  the  deposit  proceed  as 
follows :  After  having  removed  one  of  the  pans  of  a  sensitive 
beam  balance,  substitute  for  it  a  brass  rod  which  keeps  the  other 
pan  in  equilibrium.  Under  this  rod  place  a  vessel  filled  with 
pure  water  and  of  sufficient  diameter  and  depth  to  allow  of  the 
article  suspended  to  the  rod  dipping  entirely  into  the  water 
without  touching  the  sides  of  the  vessel.  Suppose  now  that 
several  dozen  spoons  of  the  same  size  and  shape  are  at  the 
same  time  to  be  provided  with  a  deposit  of  a  determined  weight, 
it  suffices  to  control  the  weight  of  the  deposit  of  a  single  spoon, 
and  when  this  has  acquired  the  necessary  deposit  all  the  other 
spoons  will  also  be  coated  with  a  deposit  of  silver  of  the  same 
thickness  as  the  test  spoon.  After  quicking  and  carefully  rinsing 
the  spoons,  one  of  them  is  suspended  to  the  brass  rod  of  the 
balance  so  that  it  dips  entirely  under  water ;  the  equilibrium  is 
then  re-established  by  placing  lead  shot  upon  the  pan  of  the 
scale,  and  edding  the  weight  corresponding  to  the  deposit  the 
spoon  is  to  receive.  Now  bring  the  weighed  spoon  together 
with  the  rest  into  the  bath,  and  proceed  with  the  silvering  pro- 
cess in  the  ordinary  manner.  After  some  time  the  weighed 
spoon  is  taken  from  the  bath,  rinsed  in  water,  and  hung  to  the 
brass  rod  of  the  scale;  if  it  does  not  restore  the  equilibrium  of 
the  latter,  it  is  returned  to  the  bath,  after  some  time  again 
weighed,  and  so  on  until  its  weight  corresponds  to  that  of  the 
lead  shot  and  weight  placed  in  the  pan  of  the  scale,  when  it  is 
assumed  that  the  balance  of  the  articles  have  also  received  their 
proper  quantity  and  that  the  operation  is  complete. 

A  more  complete  weighing  apparatus  is  the  plating  balance 


264 


ELECTRO-DEPOSITION    OF   METALS. 


first  used  by  Brandely  and  later  on  improved  by  Roseleur. 
The  apparatus,  which  is  shown  in  Fig.  117,  is  designed  for 
obtaining  deposits  of  silver  "  without  supervision  and  with  con- 

FIG.  117. 


stant  accuracy,  and  which  spontaneously  breaks  the  current 
when  the  operation  is  terminated."  It  is  manufactured  in 
various  sizes,  suitable  for  small  or  large  operations. 

It  consists  of:  I.  A  wooden  vat,  the  upper  edge  of  which 
carries  a  brass  winding-rod  having  a  binding  screw  at  one  end 
to  receive  the  positive  conducting  wire  of  the  battery ;  from  this 
rod  the  anodes  are  suspended,  which  are  entirely  immersed  in 
the  solution,  and  communicate  with  brass  cross-rods  by  means 
of  platinum  wire  hooks.  These  cross-rods  are  flattened  at  their 


DEPOSITION    OF    SILVER. 


265 


FIG.  1 1 8. 


ends  so  that  they  may  not  roll,  and  at  the  same  time  have  a 
better  contact  with  the  "  winding-rod."  2.  A  cast-iron  column 
screwed  at  its  base  to  the  side  of  the  vat,  and  which  carries  near 
the  top  two  projecting  arms  of  cast-iron,  the  extremities  of 
which  are  vertical  and  forked,  and  may  be  opened  or  closed  by 
iron  clamps.  These  forks  are  intended  for  sustaining  the  beam 
and  preventing  the  knives  from  leaving  their  bearings  under  the 
influence  of  too  violent  oscillations.  In  the 
middle  of  the  two  arms  are  two  wedge-shaped 
recesses  of  polished  steel  to  receive  the  knife 
edge?  of  the  beam.  One  of  the  arms  of  the 
column  carries  at  its  end  a  horizontal  ring  of 
iron  in  which  is  fixed  a  heavy  glass  tube  sup- 
porting a  cup  of  polished  iron  which  is  insulated 
from  the  column  (Fig.  118). 

This  cup  has  at  its  lower  part  a  small  pocket 
of  lamb-skin  or  of  India  rubber,  which  by  means 
of  a  screw  beneath  may  be  raised  or  lowered. 
This  flexible  bottom  allows  the  operator  to 
lower  or  raise  at  will  the  level  of  the  mercury 
introduced  afterwards  into  the  iron  cup.  Another 
lateral  screw  permits  connection  to  be  made  with 
the  negative  electrode.  3.  A  cast-iron  beam  carrying  in  the 
middle  two  sharp  knife-edges  of  the  best  steel  hardened  and 
polished.  At  each  extremity  there  are  two  parallel  bearings 
of  steel  separated  by  a  notch,  and  intended  for  the  knife  edges 
of  the  scale-pan  that  receives  the  weights,  and  those  of  the 
frame  supporting  the  articles  to  be  silvered.  One  of  the  arms 
of  the  beam  is  provided  with  a  stout  platinum  wire,  placed  im- 
mediately above  and  in  the  centre  of  the  cup  of  mercury. 
According  as  the  beam  inclines  one  way  or  the  other,  this  wire 
plays  in  or  out  of  the  cup.  4.  A  scale-pan  for  weights,  with 
two  knife  edges  of  cast-steel,  which  is  attached  to  four  chains 
supporting  a  wooden  pan  for  the  reception  of  weights.  A 
smaller  pan  above  is  intended  for  the  weights  corresponding  to 
that  of  the  silver  to  be  deposited.  5.  The  frame  for  support- 


266 


ELECTRO-DEPOSITION    OF   METALS. 


ing  the  articles  to  be  silvered,  which  is  also  suspended  from  two 
steel  knife  edges,  and  the  rod  of  which  is  formed  of  a  stout 
brass  tube  attached  below  to  the  brass  frame  proper,  which  last 
is  equal  in  dimensions  to  the  opening  of  the  vat,  and  supports 
the  rods  to  which  the  articles  are  suspended. 

Fig.  119  shows  a  Roseleur  plating  balance,  together  with  the 
resistance  board,  voltmeter,  and  silver  bath  ;  and  will  be  under- 
stood without  further  explanation. 

FIG.  119. 


For  calculating  the  weight  of  the  deposit  from  the  density  of 
current,  see  "  Chemical  and  Electric  Equivalents." 

When  the  articles  have  received  a  deposit  of  the  required 
weight,  they  are  treated  for  the  prevention  of  subsequent  yellow- 
ing according  to  one  of  the  methods  given  on  p.  258,  then 


DEPOSITION    OF    SILVER.  267 

scratch-brushed  with  the  use  of  decoction  of  soap-root,  plunged 
in  hot  water,  and  dried  in  sawdust. 

Articles  which  are  to  retain  the  beautiful  crystalline  dead 
white  with  which  they  come  from  the  bath  are,  without  touch- 
ing them  with  the  fingers  or  knocking  them  against  the  sides  of 
the  vessel,  plunged  into  very  hot  clean  water  and  then  sus- 
pended free  to  dry;  immediately  after  drying  they  are  to  be 
provided  with  a  thin  coat  of  kristalline  or  zapon  to  protect  the 
dead  white  coating  which  readily  turns  yellow,  and,  moreover, 
is  very  sensitive. 

The  silvered  articles  having  been  scratch-brushed,  must  finally 
be  polished,  which  may  be  effected  upon  a  fine  felt  wheel  with 
the  use  of  rouge,  but  imparting  high  lustre  by  burnishing  is  to 
be  preferred,  the  deposit  being  first  treated  with  the  steel  burn- 
isher and  then  with  the  stone  burnisher,  as  explained  on  p.  149. 
The  steel  burnisher  consists  of  a  piece  of  polished  steel  varying 
in  shape  mounted  in  a  wooden  handle.  The  operation  of  burn- 
ishing is  very  simple.  Take  hold  of  the  tool  very  near  to  the 
steel  or  stone,  and  lean  very  hard  with  it  on  those  parts  which 
are  to  be  burnished,  causing  it  to  glide  by  a  backward  and  for- 
ward movement  without  taking  it  from  the  piece.  When  it  is 
requisite  that  the  hand  should  pass  over  a  large  surface  at  once, 
without  losing  its  point  of  support  on  the  work-bench,  in  taking 
hold  of  the  burnisher  be  careful  to  place  it  just  underneath  the 
little  finger.  By  these  means  the  work  is  done  more  quickly, 
and  the  tool  is  more  solidly  fixed  in  the  hand.  During  the 
whole  process  the  tool  must  be  continually  moistened  with 
soap-suds. 

In  some  establishments  in  which  plated  table-ware  in  large 
quantity  is  turned  out,  ingeniously  devised  burnishing  machines 
driven  by  power  are  in  use,  by  which  much  of  the  manual  labor 
is  spared.  The  knife,  spoon,  etc.,  each  supported  by  its  tips  in 
a  suitable  holder,  are  very  slowly  rotated,  while  the  burnishing 
tool  moves  quickly  over  the  surface,  performing  the  work 
rapidly  and  satisfactorily. 

When  the  burnishing  is  completed,  the  surface  is  wiped  off 


268  ELECTRO-DEPOSITION    OF    METALS. 

longitudinally  with  an  old,  soft  calico  rag ;  sawdust,  hard  cloth, 
and  tissue  paper  produce  streaks. 

B.  Ordinary  silvering. — The  operations  the  objects  which  are 
to  receive  a  deposit  of  less  thickness  have  to  undergo,  are  ex- 
actly the  same  as  those  described  under  silvering  by  weight,  the 
only  difference  being  that  for  quicking  a  weaker  solution  (15  to 
3 1  grains  of  nitrate  of  mercury  to  I  quart  of  water)  or  very 
dilute  solution  of  potassium- mercury  cyanide  is  used,  and  that 
the  objects  remain  in  the  bath  for  a  shorter  time.  As  previ- 
ously mentioned,  iron,  steel,  zinc,  tin,  etc.,  should  first  be 
coppered  or  brassed ;  however,  tin  in  its  alloys  may  also  be 
directly  silvered  in  the  silver  bath,  but  a  larger  excess  of  potas- 
sium cyanide  is  required  than  for  copper,  brass,  or  German 
silver. 

According  to  Dr.  William  H.  Wahl,  in  the  United  States,  the 
practice  of  previous  coppering  is  not  adopted  either  with  Bri- 
tannia metal  or  steel.  The  practice  of  different  establishments 
of  cleansing  their  work  differs  somewhat,  but  all  aim  at  the 
same  result,  viz.,  to  secure  a  smooth  adhering  coating  of  metal 
upon  an  inferior  base. 

The  practice  of  the  Meriden  Britannia  Co.'s  works  at  Meriden, 
Conn.,  as  observed  by  Dr.  William  H.  Wahl,  is  substantially  as 
follows:  With  Britannia  or  "  white  metal :"  The  article  is  first 
cleansed  of  all  grease  by  immersion  in  boiling  alkali ;  then  into 
dilute  muriatic  acid;  then  into  a  ''striking"  solution,  viz.,  a 
weak  cyanide  of  silver  solution  with  a  large  proportion  of  free 
cyanide  of  potassium,  and  a  large  silver  anode  operated  with  a 
very  strong  electric  current.  The  purpose  of  immersion  in  this 
solution  is  to  effect  an  instantaneous  deposit  of  silver  on  the 
metal,  to  better  insure  a  perfect  coating  in  the  silver  bath 
proper.  The  articles  remain  in  the  "  striking  "  solution  for  a 
few  seconds  only,  as  its  action,  owing  to  the  large  proportion 
of  free  cyanide  it  contains,  is  very  prompt,  and  as  soon  as  they 
have  received  a  thin  coating,  which  takes  place  almost  imme- 
diately, they  are  removed  to  the  electro-plating  bath,  where 
they  remain  until  they  have  received  the  proper  coating  of 


DEPOSITION   OF   SILVER.  269 

silver.  In  many  cases,  especially  with  articles  of  considerable 
size,  cleansing  in  boiling  alkali  must  be  supplemented  by  scratch- 
brushing,  in  which  case  the  acid  dip  may  be  dispensed  with,  and 
the  article,  after  thorough  rinsing  and  dipping  in  alkali  to  re- 
move finger-marks,  is  immersed  at  once  in  the  "  striking  "  solu- 
tion. 

German  silver  or  nickel  articles  are  first  cleansed  in  boiling 
alkali,  washed,  then  dipped  in  a  mixture  of  two-thirds  sulphuric 
acid  and  one-third  nitric  acid,  then  into  quicking  solution,  then 
into  the  "  striking"  solution,  and  from  this  into  the  plating  bath. 

Steel  articles  are  cleansed  in  boiling  alkali,  rinsed,  dipped  in 
muriatic  acid,  then  in  the  "striking"  solution,  and  from  this 
into  the  plating  bath.  In  case  the  articles  require  scouring  the 
acid  dip  is  dispensed  with.  For  steel  two  "  striking  "  solutions 
are  used,  one  somewhat  richer  in  silver  than  the  other,  the 
weaker  solution  being  used  first. 

With  the  William  Rogers  Manufacturing  Co.,  Hartford,  Conn., 
the  following  is  the  general  outline  of  the  methods  in  use  for 
preparing  work  for  plating:  — 

For  cleansing  (steel)  cutlery. — Immersion  in  boiling  alkali  for 
the  removal  of  grease ;  scouring;  rinsing;  dipping  into  strong 
muriatic  acid  ;  then  for  a  few  seconds  in  a  silver  "  striking " 
solution ;  then  in  a  plating  bath  until  the  required  amount  of 
silver  is  deposited. 

The  formula  for  the  "  striking  "  solution,  which  will  be  given 
later  on,  is  low  in  silver,  rich  in  cyanide,  and  worked  with  a 
strong  current  and  silver  anode. 

Nickel-silver  ( German  silver)  for  spoons. — Immerse  in  boil- 
ing alkali;  scouring,  if  necessary  rinsing  in  water;  immersion 
in  acid  mixture,  composed  of  two-thirds  sulphuric  acid  and  one- 
third  nitric  acid;  dipping  in  weak  quicking  solution  (either 
very  dilute  potassium-mercury  cyanide  or  acidulated  nitrate  of 
mercury)  ;  immersion  for  a  few  seconds  in  the  silver  "  striking" 
solution ;  and  from  this  into  the  plating  bath. 

Britannia  metal  {hollow-ware) . — Cleansing  in  alkali  as  above  ; 
rinsing  in  water ;  again  immersing  in  alkali  to  remove  finger- 


2/0  ELECTRO-DEPOSITION    OF   METALS. 

marks,  if  necessary,  immersing  in  the  "striking"  solution,  and 
from  this  into  the  plating  solution.  A  quicking  solution  for 
Britannia,  sometimes  employed,  is  composed  of  a  strong  solu- 
tion of  sal  ammoniac  and  corrosive  sublimate,  into  which  the 
articles  are  dipped  after  cleansing  in  potash. 

The  silver  "  striking  "  solution,  as  used  by  the  Wm.  Rogers 
Manufacturing  Co.,  of  Hartford,  Conn.,  is  composed  as  follows  : — 

Rogers' s  "  striking"  solution. — Cyanide  of  potassium  6  ozs., 
silver  y%  oz.,  water  I  gallon.  Use  a  strong  current. 

Meriden  Company's  "  striking  solution." — Cyanide  of  potas- 
sium 12  to  1 6  ozs.,  silver  8  to  10  dwts.,  water  I  gallon. 

The  plating  solution  commonly  employed  by  the  Wm.  Rogers 
Manufacturing  Co.  has  the  following  composition :  Cyanide  of 
potassium  6  ozs.,  silver  (in  chlorate)  4  ozs.,  water  I  gallon. 

The  usual  formula  of  the  Meriden  Britannia  Co.  has  the  fol- 
lowing proportions  :  Cyanide  of  potassium  12  ozs.,  silver  3  ozs., 
water  i  gallon. 

In  order  to  secure  an  extra  heavy  coating  of  silver  on  the 
convex  surfaces  of  spoons  and  forks,  which,  being  subject  to 
greater  wear  than  the  other  parts,  require  extra  protection,  the 
Meriden  Britannia  Co.  uses  a  frame  in  which  the  articles  sup- 
ported therein  by  their  tips  are  placed  horizontally  in  a  shallow 
silver  bath,  and  immersed  just  deep  enough  to  allow  the  pro- 
jecting convexities  to  dip  into  the  bath.  By  this  artifice  these 
portions  are  given  a  second  coating  of  silver  of  any  desired 
thickness.  This  mode  of  procedure,  which  is  termed  "sec- 
tional" plating,  accomplishes  the  intended  purpose  nicely  and 
satisfactorily.  In  some  establishments  the  silvered  forks  and 
spoons  are  placed  between  plates  of  gutta-percha  of  corre- 
sponding shape,  and  held  together  by  rubber  bands.  In  these 
plates  the  portions  to  be  provided  with  an  extra  coating  of 
silver  are  cut  out.  By  suspending  the  forks  and  spoons  thus 
protected  in  the  bath,  the  unprotected  places  receive  a  further 
layer  of  silver,  the  outlines  of  which  are  later  on  smoothed 
down  with  burnishers. 

"Stopping-Off" — Stopping-off  is  the  manipulation  by  which 


DEPOSITION    OF    SILVER.  2/1 

certain  parts  of  a  metallic  article,  which  are  already  covered 
with  an  electro -deposit  on  its  entire  surface,  are  coated  with  an- 
other metal.  For  instance,  if  it  is  desired  to  gild  the  parts  in 
relief  of  an  article,  the  other  portions  are  "  stopped-off,"  and 
vice  versa.  Stopping-off  varnish  is  prepared  by  dissolving 
asphalt  or  dammar  with  an  addition  of  mastic  in  oil  of  tur- 
pentine. Apply  with  a  brush,  and  after  thoroughly  drying  the 
articles  in  the  drying-chamber,  place  them  for  an  hour  in  very 
cold  water,  whereby  the  varnish  hardens  completely.  After 
plating,  the  varnish  is  removed,  best  with  benzine,  the  article 
plunged  in  hot  water,  and  dried  in  saw-dust. 

For  a  varnish  that  will  resist  the  solvent  power  of  the  hot 
alkaline  gilding  liquid,  Gore  recommends  the  following  compo- 
sition :  Translucent  rosin  10  parts,  yellow  beeswax  6,  extra-fine 
red  sealing-wax  4,  finest  polishing  rouge  3. 

Silvering  by  contact,  by  immersion,  and  cold  silvering  with 
paste. — For  silvering  by  contact  with  zinc,  the  bath  prepared 
according  to  formula  II.  may  be  used,  adding  about  17  grains 
more  of  potassium  cyanide  per  quart.  The  articles  are  to  be 
prepared  in  the  same  manner  as  for  silvering  by  weight,  and 
quicked  in  a  weak  quicking  solution.  Before  placing  the  arti- 
cles in  the  bath  they  are  wrapped  round  with  bright  zinc  wire, 
or  are  brought  in  contact  while  in  the  bath  with  a  bright  strip 
of  zinc,  care  being  had  to  frequently  change  the  points  of  con- 
tact to  prevent  the  formation  of  stains.  As  previously  men- 
tioned, by  the  contact  of  the  metal  to  be  silvered  with  the 
electro-positive  zinc,  a  weak  current  is  produced  which  effects 
the  deposition  of  the  silver,  but  this  taking  place  very  slowly,  it 
is  best  to  heat  the  silver  bath.  Silver  being  at  the  same  time 
deposited  upon  the  zinc,  the  latter  must  be  frequently  freed 
from  the  deposit  and  brightened  by  means  of  a  file  or  emery 
paper. 

By  contact  with  zinc,  silver  may  also  be  deposited  in  one  of 
the  following  baths  for  silvering  by  immersion;  Crystallized 
nitrate  of  silver  5.64  drachms,  98  per  cent,  potassium  cyanide 
1.23  ozs.,  water  I  quart.  To  prepare  the  bath  dissolve  the 


£72  ELECTRO-DEPOSITION   OF   METALS. 

silver  salt  in  I  pint  of  distilled  water,  then  the  potassium 
cyanide  in  the  remaining  pint  of  water,  and  mix  the  two  solu- 
tions. The  bath  is  heated  in  a  porcelain  or  enameled  iron 
vessel  to  between  176°  and  194°  F.,  and  the  thoroughly 
cleansed  and  pickled  objects  are  immersed  in  it  until  uniformly 
coated  ;  previous  quicking  is  not  required.  The  deposit  is  lus- 
trous if  the  articles  are  left  but  a  short  time  in  the  bath,  but 
becomes  dull  when  they  remain  longer ;  in  the  first  case  the 
deposit  is  a  mere  film,  and,  while  it  is  somewhat  thicker  in  the 
latter,  it  can  under  no  circumstances  be  called  solid. 

The  bath  gradually  works  less  effectively  and  finally  ceases 
to  silver,  when  it  may  be  attempted  to  restore  its  action  by  the 
addition  of  2^  to  5^  drachms  of  potassium  cyanide  per  quart. 
Should  this  prove  ineffectual,  the  content  of  silver  is  nearly 
exhausted,  and  the  bath  is  evaporated  to  dryness,  and  the 
residue  added  to  the  silver  waste.  Frequent  refreshing  of  the 
bath  with  silver  salt  cannot  be  recommended,  the  silvering 
always  turning  out  best  in  a  fresh  bath. 

A  solution  of  nitrate  of  silver  in  sodium  sulphide  is,  accord- 
ing to  Roseieur,  very  suitable  for  silvering  by  immersion.  The 
solution  is  prepared  by  pouring  into  a  moderately  concentrated 
solution  of  sodium  sulphide,  with  constant  stirring,  solution  of 
a  silver  salt  until  the  precipitate  of  silver  sulphide  formed  be- 
gins to  be  dissolved  with  difficulty.  This  bath  can  be  used 
cold  or  warm,  fresh  solution  of  silver  being  added  when  it  com- 
mences to  lose  its  effect.  If,  however,  the  bath  is  not  capable 
of  dissolving  the  silver  sulphide  formed,  concentrated  solution 
of  sodium  sulphide  has  to  be  added. 

For  the  preparation  of  the  solution  of  sodium  sulphide,  Rose- 
ieur recommends  the  following  method  :  — 

Into  a  tall  vessel  of  glass  or  porcelain  (Fig.  120)  introduce  5 
quarts  of  water  and  4  pounds  of  crystallized  soda,  after  pouring 
in  mercury  about  an  inch  or  so  deep  to  prevent  the  glass  tube 
through  which  the  sulphurous  acid  is  introduced  from  being 
stopped  up  by  crystals.  The  sulphurous  acid  is  evolved  by  heat- 
ing copper  turnings  with  concentrated  sulphuric  acid,  washing 


DEPOSITION    OF   SILVER,  2/3 

the  gas  in  a  Woulff  bottle  filled  an  inch  or  so  deep  with  water, 
and  introducing  it  into  the  bottle  containing  the  soda  solution, 
as  shown  in  the  illustration.  A  part  of  the  soda  becomes  trans- 
formed into  sodium  sulphide,  which  dissolves,  and  a  part  is  pre- 
cipitated as  carbonate.  The  latter,  however,  is  transformed 
into  sodium  sulphide  by  the  continuous  action  of  sulphurous 
acid,  and  carbonic  acid  gas  escapes  with  effervesence.  When  all 
has  become  dissolved,  the  passage  of  sulphurous  acid  should  be 
continued  until  the  liquid  slightly  reddens  blue  litmus-paper, 
and  then  allowed  to  stand  aside  for  24  hours.  At  the  end  of 

/• 

FIG.  1 20. 


that  time  a  certain-  quantity  of  crystals  will  be  found  upon  the 
mercury,  and  the  liquid  above,  more  or  less  colored,  constitutes 
the  sodium  sulphide  of  the  silvering  bath.  The  liquid  sodium 
sulphide  thus  prepared  should  be  stirred  with  a  glass  rod,  to 
eliminate  the  carbonic  acid  which  may  still  remain  in  it.  The 
liquid  should  then  be  again  tested  with  litmus-paper  ;  and  if  the 
blue  color  is  strongly  reddened,  carbonate  of  soda  is  cautiously 
added,  little  by  little,  in  order  to  neutralize  the  excess  of  sul- 
phurous acid.  On  the  other  hand,  if  red  litmus-paper  becomes 
blue,  too  much  alkali  is  present,  and  more  sulphurous  acid  gas 
18 


274  ELECTRO-DEPOSITION   OF   METALS. 

must  be  passed  through  the  liquid,  which  is  in  the  best  condi- 
tion for  our  work  when  it  turns  litmus-paper  violet  or  slightly 
red.  The  solution  should  mark  from  22°  to  26°  Be.,  and 
should  not  come  in  contact  with  iron,  zinc,  tin,  or  lead. 

As  will  be  seen,  this  mode  of  preparing  the  sodium  sulphide 
solution  is  somewhat  troublesome,  and  it  is,  therefore,  recom- 
mended to  proceed  as  follows:  Prepare  a  saturated  solution  of 
commercial  sodium  sulphide;  the  solution  will  show  an  alka- 
line reaction,  the  commercial  salt  frequently  containing  some 
sodium  carbonate.  To  this  solution  add,  with  stirring,  solution 
of  bisulphite  of  sodium  saturated  at  122°  F.,  until  blue  litmus- 
paper  is  slightly  reddened.  Then  add  to  this  solution  concen- 
trated solution  of  nitrate  of  silver  until  the  flakes  of  silver  sul- 
phide separated  begin  to  dissolve  with  difficulty. 

The  immersion  bath,  prepared  according  to  one  or  the  other 
method,  works  well  and  has  the  advantage  of  producing  silver- 
ing of  a  beautiful  lustre,  such  as  is  desirable  for  many  cheap 
articles.  By  allowing  the  articles  to  remain  for  a  longer  time 
in  the  bath,  the  lustrous  deposit  becomes  dull.  For  the  pro- 
duction of  a  lustrous  coating  the  bath  should  always  be  used 
cold.  It  must  further  be  protected,  as  much  as  possible,  from 
the  light,  as  otherwise  gradual  decomposition  takes  place. 

According  to  Dr.  Ebermayer  a  silver-immersion  bath  for 
lustrous  silvering  is  prepared  as  follows:  Dissolve  1.12  ozs.  of 
nitrate  of  silver  in  water,  and  precipitate  the  solution  with 
caustic  potash.  Thoroughly  wash  the  silver  oxide  which  is 
precipitated,  and  dissolve  it  in  I  quart  of  water  which  contains 
3.52  ozs.  of  potassium  cyanide  in  solution,  and  finally  dilute  the 
whole  with  I  quart  more  of  water.  For  silvering,  the  bath  is 
heated  to  the  boiling  point,  and  the  silver  withdrawn  may  be 
replaced  by  the  addition  of  moist  silver  oxide  as  long  as  com- 
plete dissolution  takes  place.  When  the  silvering  is  no  longer 
beautiful  and  of  a  pure  white  color,  the  bath  is  useless  and  is 
then  evaporated.  Experiments  with  a  bath  prepared  according 
to  the  above  directions  were  not  satisfactory,  the  coating  being 
dull  and  adhering  badly. 


DEPOSITION    OF   SILVER.  2/5 

For  silvering  articles,  especially  those  composed  of  the  various 
alloys  of  copper,  without  the  use  of  a  current,  the  following 
process  is  recommended  in  "  Edelmetallindustrie."  Dissolve 
silver  in  nitric  acid  with  the  assistance  of  the  sand  or  water  bath, 
and  convert  it  into  chloride  of  silver  by  carefully  adding  hydro- 
chloric acid  or  common  salt  solution  until,  after  repeated  stir- 
ring and  allowing  to  settle,  no  more  precipitate  is  formed^ 
Now  let  the  mixture  repose,  then  pour  off  the  supernatant  fluid 
and  wash  the  white  caseous  precipitate  until  litmus- paper  is  no> 
longer  reddened  by  the  wash-water.  Keep  the  chloride  of  sil- 
ver thus  obtained  in  wide-mouthed  black  bottles.  Now  prepare 
in  glazed  pots  two  baths  as  follows:  i.  A  potassium-cyanide 
bath  by  dissolving  1 1  /^  drachms  of  chloride  of  silver  and  2  ozs. 
of  potassium  cyanide  in  about  10  quarts  of  water,  and  heating 
the  mixture  to  the  boiling  point.  2.  A  salt  bath  consisting  of 
10  quarts  of  water,  1 1  Ibs.  of  common  salt,  1 1  Ibs.  of  cream  of 
tartar,  and  4^  ozs.  of  chloride  of  silver.  Boil  the  mixture, 
with  constant  stirring,  for  one  hour,  and  when  cold  pour  it  into 
another  pot,  in  which  it  may  be  kept.  The  articles  to  be 
treated  are  cleansed  by  treating  them  with  dilute  hydrochloric 
acid.  They  are  next  pickled  by  dipping  them  in  nitric  acid, 
and  finally  plunged  into  a  bright- dipping  bath,  consisting  of 
nitric  acid,  a  small  quantity  of  hydrochloric  acid  and  a  trace  of 
lamp-black.  They  are  then  thoroughly  rinsed  off,  and  thrown 
into  water  containing  a  small  quantity  of  cream  of  tartar,  where 
they  remain  until  they  are  silvered.  The  water  must  not  be 
warm  and  the  articles  should  not  remain  in  it  too  long,  other- 
wise they  will  tarnish  and  it  will  be  impossible  to  obtain  a  pure 
silvering.-  The  articles  thus  prepared  are  first  brought  into  the 
potassium-cyanide  bath  and  gently  agitated,  when  they  become 
immediately  coated  with  a  thin  film  of  silver.  They  are  then 
rinsed  and  brought  into  a  dilute  salt  bath,  prepared  by  adding 
water  to  a  portion  of  the  salt  given  under  2,  where  they  remain 
until  they  have  acquired  a  gray-white  or  yellowish-white  color. 
They  are  then  rinsed,  returned  to  the  potassium-cyanide  bath, 
again  rinsed  and  thrown  into  clean  water,  or  dried  in  sawdust. 


2/6  ELECTRO-DEPOSITION    OF   METALS. 

Each  rinsing  must  be  effected  in  a  different  vessel,  The  two 
baths  are  very  lasting  and  require  only  a  periodical  addition  of 
potassium  cyanide  (when  the  articles  on  being  immersed  be- 
come black,  which  turns  slov\ly  to  white)  or  of  chloride  of  sil- 
ver (when  the  articles  show  a  yellowish-white  color).  When 
the  dilute  salt  bath  becomes  too  weak,  a  fresh  quantity  of  the 
the  salt  bath  is  added  by  means  of  a  wooden  spoon.  The 
potassium-cyanide  bath  must  be  shaken  every  day.  During 
the  process  of  silvering  the  potassium-cyanide  bath  is  to  be 
kept  at  between  176°  and  194°  F.,  and  the  salt  bath  at  above 
212°  F.  The  potassium-cyanide  bath  should  only  be  boiled 
before  use,  when  making  a  fresh  addition  of  potassium  cyanide, 
or  of  chloride  of  silver.  The  silvering  obtained  with  the  use  of 
these  vats  is  pure-white,  cheap,  and  durable. 

The  process  of  coating  with  a  thin  film,  or  rather  coloring 
with  silver,  small  articles  such  as  hooks  and  eyes,  pins,  etc., 
differs  from  the  above-described  immersion  method,  which 
effects  the  silvering  in  a  few  seconds,  in  that  the  articles  require 
to  be  boiled  for  a  longer  time.  The  process  is  as  follows : 
Prepare  a  paste  from  14.11  drachms  of  nitrate  of  silver,  pre- 
cipitated as  chloride  of  silver;  44  ounces  of  cream  of  tartar, 
and  a  like  quantity  of  common  salt,  by  precipitating  the  solu- 
tion of  the  nitrate  of  silver  with  hydrochloric  acid,  washing  the 
chloride  of  silver  and  mixing  it  with  the  above-mentioned 
quantities  of  cream  of  tartar  and  common  salt,  and  sufficient 
water  to  a  paste,  which  is  kept  in  a  dark  glass  vessel  to  prevent 
the  chloride  of  silver  from  being  decomposed  by  the  light. 
Small  articles  of  copper  or  brass  are  first  freed  from  grease,  and 
pickled.  Then  heat  in  an  enameled  kettle  3  to  5  quarts  of 
rain-water  to  the  boiling-point;  add  2  or  3  heaping  teaspoon- 
fuls  of  the  above-mentioned  paste,  and  bring  the  metallic 
objects  contained  in  a  stoneware  sieve  into  the  bath  and  stir 
them  diligently  with  a  rod  of  glass  or  wood.  Before  placing  a 
fresh  lot  of  articles  in  the  bath  additional  silver  paste  must  be 
added.  If  finally  the  bath  acquires  a  greenish  color,  caused  by 
•dissolved  copper,  it  is  no  longer  suitable  for  the  purpose,  and  is 
then  evaporated  and  added  to  the  silver  residues. 


DEPOSITION    OF    SILVER.  277 

Cold  silvering  with  paste. — In  this  process,  an  argentiferous 
paste,  composed  as  given  below,  is  rubbed,  by  means  of  the 
thumb,  a  piece  of  soft  leather  or  rag,  upon  the  cleansed  and 
pickled  metallic  surface  (copper,  brass,  or  other  alloys  of 
copper)  until  it  is  entirely  silvered.  The  paste  may  also  be 
rubbed  in  a  mortar  with  some  water  to  a  uniform  thinly  fluid 
mass,  and  applied  with  a  brush  to  the  surface  to  be  silvered. 
By  allowing  the  paste  to  dry  naturally,  or  with  the  aid  of  a 
gentle  heat,  the  silvering  appears.  The  application  of  the  paste 
by  means  of  a  brush  is  chiefly  made  use  of  for  decorating  with 
silver  articles  thinly  gilded  by  immersion.  For  articles  not 
gilded,  the  above-mentioned  rubbing  on  of  the  stiff  paste  is  to 
be  preferred. 

Composition  of  argentiferous  pastes. — I.  Silver  in  the  form  of 
freshly  precipitated  chloride  of  silver*  0.35  oz.,  common  salt 
0.35  oz.,  potash  0.7  oz.,  whiting  0.52  oz.,  and  water  a  sufficient 
quantity  to  form  the  ingredients  into  a  stiff  paste. 

II.  Silver  in  the  form  of  freshly  precipitated  chloride  of  silver* 
0.35  oz.,  potassium  cyanide  1.05  oz.,  sufficient  water  to  dissolve 
these  two  ingredients  to  a  clear  solution,  and  enough  whiting  to 
form  the  whole  into  a  stiff  paste.  This  paste  is  also  excellent 
for  polishing  tarnished  silver ;  it  is,  however,  poisonous. 

The  following  composition,  which  is  not  poisonous,  does  ex- 
cellent service :  Silver  in  the  form  of  chloride  of  silver  0.35  oz., 
cream  of  tartar  0.7  oz.,  common  salt  0.7  oz.,  and  sufficient  water 
to  form  the  mixture  of  the  ingredients  into  a  stiff  paste. 

Another  composition  is  as  follows :  Chloride  of  silver  I  part, 
pearl-ash  3,  common  salt  i^,  whiting  I,  and  sufficient  water  to 
form  a  paste.  Apply  the  latter  to  the  metal  to  be  silvered  and 
rub  with  a  piece  of  soft  leather.  When  the  metal  is  silvered, 
wash  in  water  to  which  a  small  quantity  of  washing  soda  has 
been  added. 

Graining. — In  gilding  parts  of  watches,  gold  is  seldom  di- 
rectly applied  upon  the  copper ;  there  is  generally  a  preliminary 

*  From  0.56  oz.  of  nitrate  of  silver. 


-278  ELECTRO-DEPOSITION    OF   METALS. 

operation  called  graining,  by  which  a  grained  and  slightly  dead 
appearance  is  given  to  the  articles.  Marks  of  the  file  are  ob- 
literated by  rubbing  upon  a  whetstone,  and  lastly  upon  an  oil- 
stone. Any  oil  or  grease  is  removed  by  boiling  the  parts  for  a 
few  minutes  in  a  solution  of  10  parts  of  caustic  soda  or  potash 
in  100  of  water,  which  should  wet  them  entirely  if  all  the  oil 
has  been  removed.  The  articles  being  threaded  upon  a  brass 
wire,  cleanse  them  rapidly  in  the  acid  mixture  for  a  bright 
lustre,  and  dry  them  carefully  in  white  wood  sawdust.  The 
pieces  are  fastened  upon  the  even  side  of  a  block  of  cork  by 
brass  pins  with  flat  heads.  The  parts  are  then  thoroughly 
rubbed  over  with  a  brush  entirely  free  from  grease,  and  dipped 
into  a  paste  of  water  and  very  fine  pumice-stone  powder.  Move 
the  brush  in  circles,  in  order  not  to  rub  one  side  more  than  the 
other ;  thoroughly  rinse  in  cold  water,  and  no  particle  of  pumice- 
stone  should  remain  upon  the  pieces  or  the  cork.  Next  place 
the  cork  and  the  pieces  in  a  weak  mercurial  solution,  composed 
of  water  2^  gallons,  nitrate  or  binoxide  of  mercury  yT  oz.,  sul- 
phuric acid  i  oz.,  which  slightly  whitens  the  copper.  The 
pieces  are  passed  quickly  through  the  solution  and  then  rinsed. 
This  operation  gives  strength  to  the  graining,  which  without  it 
possesses  no  adherence. 

The  following  preparations  may  be  used  for  graining:  I. 
Silver  in  impalpable  powder  2  ozs.,  finely  pulverized  cream  of 
tartar  20  ozs.,  common  salt  4  Ibs.  II.  Silver  powder  I  oz., 
cream  of  tartar  4  to  5  ozs.,  common  salt  13  ozs.  III.  Silver 
powder,  common  salt,  and  cream  of  tartar,  equal  parts  by 
weight  of  each.  The  mixture  of  the  three  ingredients  must  be 
thorough  and  effected  at  a  moderate  and  protracted  heat.  The 
graining  is  the  coarser  the  more  common  salt  there  is  in  the 
mixture,  and  it  is  the  finer  and  more  condensed  as  the  propor- 
tion of  cream  of  tartar  is  greater,  but  it  is  then  more  difficult  to 
scratch-brush.  The  silver  powder  is  obtained  as  follows  :  Dis- 
solve in  a  glass  or  porcelain  vessel  2/$  oz.  of  crystallized  nitrate 
of  silver  in  2^/2  gallons  of  distilled  water,  and  place  5  or  6 
ribands  of  cleansed  copper,  ^  inch  wide,  in  the  solution. 


DEPOSITION    OF   SILVER.  2/9 

These  ribands  should  be  long  enough  to  allow  of  a  portion  of 
them  being  above  the  liquid.  The  whole  is  kept  in  a  dark 
place,  and  from  time  to  time  stirred  with  the  copper  ribands. 
This  motion  is  sufficient  to  loosen  the  deposited  silver,  and 
present  fresh  surfaces  to  the  action  of  the  liquor.  When  no 
more  silver  deposits  on  the  copper,  the  operation  is  complete, 
and  there  remains  a  blue  solution  of  nitrate  of  copper.  The 
silver  powder  is  washed  by  decantation  or  upon  a  filter  until 
there  remains  nothing  of  the  copper  solution, 

For  the  purpose  of  graining,  a  thin  paste  is  made  of  one  of 
the  above  mixtures  and  water,  and  spread  by  means  of  a  spatula 
upon  the  watch  parts  held  upon  the  cork.  The  cork  itself  is 
placed  upon  an  earthenware  dish,  to  which  a  rotating  move- 
ment is  imparted  by  the  left  hand.  An  oval  brush  with  close 
bristles,  held  in  the  right  hand,  rubs  the  watch  parts  in  every 
direction,  but  always  with  a  rotary  motion.  A  new  quantity  of 
paste  is  added  two  or  three  times  and  rubbed  in  the  manner  in- 
dicated. The  more  the  brush  and  cork  are  turned  the  rounder 
becomes  the  grain,  which  is  a  good  quality,  and  the  more  paste 
added  the  larger  the  grain.  When  the  desired  grain  is  obtained 
the  pieces  are  washed  and  scratch-brushed.  The  brushes  em- 
ployed are  of  brass  wire,  as  fine  as  hair  and  very  stiff  and 
springy.  It  is  necessary  to  anneal  them  upon  an  even  fire  to 
different  degrees ;  one  soft  or  half-annealed  for  the  first  opera- 
tion or  uncovering  the  grain ;  one  harder  for  bringing  up  the 
lustre;  and  one  very  soft  or  fully  annealed,  used  before  gilding 
for  removing  any  marks  which  may  have  been  made  by  the 
preceding  tool,  and  for  scratch-brushing  after  gilding,  which, 
like  the  graining,  must  be  done  by  giving  a  rotary  motion  to 
the  tool.  If  it  happens  that  the  same  watch  part  is  composed 
of  copper  and  steel,  the  latter  metal  requires  to  be  preserved 
against  the  action  of  the  cleansing  acids  and  of  the  graining 
mixture  by  a  composition  called  resist.  This  consists  in  cover- 
ing the  pinions  and  other  steel  parts  with  a  fatty  composition 
which  is  sufficiently  hard  to  resist  the  tearing  action  of  the 
bristle  and  wire  brushes,  and  insoluble  in  the  alkalies  of  the  gild- 


280  ELECTRO-DEPOSITION    OF   METALS. 

ing  bath.  A  good  composition  is :  Yellow  wax  2  parts  by 
weight,  translucent  rosin  3^,  extra  fine  red  sealing-wax  I  J^ , 
polishing  rouge  I.  Melt  the  rosin  and  sealing-wax  in  a  porce- 
lain dish,  upon  a  water-bath,  and  afterwards  add  the  yellow  wax. 
When  the  whole  is  thoroughly  fluid,  gradually  add  the  rouge 
and  stir  with  a  wooden  or  glass  rod.  Withdraw  the  heat,  but 
continue  the  stirring  until  the  mixture  becomes  solid,  otherwise 
all  the  rouge  will  fall  to  the  bottom.  The  flat  parts  to  receive 
this  resist  are  slightly  heated  and  then  covered  with  the  mixture, 
which  melts  and  is  easily  spread.  For  covering  steel  pinions 
employ  a  small  gouge  of  copper  or  brass  fixed  to  a  wooden 
handle.  The  metallic  part  of  the  gouge  is  heated  upon  an  alco- 
hol lamp,  and  a  small  quantity  of  resist  is  taken  with  it.  The 
composition  soon  melts,  and  by  turning  the  tool  around  the 
steel  pinion  thus  becomes  coated.  Use  a  scratch-brush  with 
long  wires,  as  their  flexibility  prevents  the  removal  of  the  com- 
position. When  the  resist  is  to  be  removed  after  gilding,  put 
the  parts  into  warm  oil  or  tepid  turpentine,  then  into  a  very  hot 
soap-water  or  alkaline  solution;  and,  lastly,  into  fresh  water. 
Scratch-brush  and  dry  in  warm,  white  wood  sawdust.  The 
holes  of  the  pinions  are  cleansed  and  polished  with  small  pieces 
of  very  white,  soft  wood,  the  friction  of  which  is  sufficient  to 
restore  the  primitive  lustre.  The  gilding  of  parts  of  copper  and 
steel  requires  the  greatest  care,  as  the  slightest  rust  destroys 
their  future  usefulness.  Should  some  gold  deposit  upon  the 
steel,  it  should  be  removed  by  rubbing  with  a  piece  of  wood 
and  impalpable  pumice  dust,  tin-putty,  or  rouge. 

The  gilding  of  the  grained  watch  parts  is  effected  in  a  bath 
prepared  according  to  formula  I.  or  III.,  given  under  "  Deposi- 
tion of  Gold." 

The  silvering  of  fine  copper  wire  is  effected  in  an  apparatus 
similar  to  that  shown  in  Fig.  1 12,  p.  21 1,  a  reservoir  containing 
potassium  cyanide  solution  for  pickling  the  cleansed  wire  being 
added  and  placed  in  front  of  the  silver  bath.  Lustre  is  im- 
parted to  the  silvered  wire  by  drawing  through  a  draw-plate. 
Further  details  will  be  found  under  "  Gilding." 


DEPOSITION    OF    SILVER.  28 1 

Incrustations  with  silver,  gold,  and  other  metals. — By  incrust- 
ing  is  understood  the  inlaying  of  depressions,  produced  by  en- 
graving or  etching  upon  a  metallic  body,  with  silver,  gold,  and 
other  metals,  such  as  Japanese  incrustations,  which  are  made  by 
mechanically  pressing  the  silver  or  gold  into  the  depressions. 
Such  incrustations,  however,  can  also  be  produced  by  electro- 
deposition,  the  process  being  as  follows :  The  design  which  is 
to  be  incrusted  upon  a  metal  is  executed  with  a  pigment  of 
white-lead  and  glue-water  or  gum-water.  The  portion  not  cov- 
ered by  the  design  is  then  coated  with  stopping-off  varnish.  The 
article  is  next  placed  in  dilute  nitric  acid,  whereby  the  pigment 
is  first  dissolved,  and  next  the  surface  etched,  which  is  allowed 
to  progress  to  a  certain  depth.  Etching  being  finished,  the 
article  is  washed  in  an  abundance  of  water  and  immediately 
brought  into  a  silver  or  gold  bath,  in  which  by  the  action  of  the 
current  the  exposed  places  are  filled  up  with  metal.  This  being 
done,  the  "  stopping-off "  varnish  is  removed  with  benzine,  the 
surface  ground  smooth,  and  polished.  In  this  manner  one 
article  may  be  incrusted  with  several  metals  ;  for  instance,  brass 
may  be  incrusted  with  copper,  silver,  and  gold,  and  by  oxidizing 
or  coloring  portions  of  the  copper  beautiful  effects  can  be  pro- 
duced. The  principal  requisites  for  these  incrustations  are 
manual  skill  and  much  patience ;  expensive  apparatus  is  not 
required,  every  skilled  electro-plater  being  able  to  execute  the 
work. 

Imitation  of  niel  or  nielled  silvering. — By  nielling  is  under- 
stood the  inlaying  of  designs,  produced  either  by  engraving  or 
stamping,  with  a  black  mixture  of  metallic  sulphides.  The 
nielling  powder  is  prepared  by  melting  silver  20  parts  by  weight, 
copper  90  parts  and  lead  150  parts.  To  the  liquid  metallic 
mass  add  26^  ozs.  of  sulphur  and  ^  oz.  of  sal  ammoniac, 
quickly  cover  the  crucible,  and  continue  heating  until  the  excess 
of  sulphur  is  volatilized.  Then  pour  the  contents  of  the  cruci- 
ble into  another  crucible,  the  bottom  of  which  is  covered  about 
y^  inch  deep  with  flowers  of  sulphur,  cover  the  crucible  and  allow 
the  mixture  to  cool.  When  cold  bring  the  contents  once  more 


282  ELECTRO-DEPOSITION    OF   METALS. 

to  the  fusing  point  and  pour  the  fused  mass  in  a  thin  stream 
into  a  bucket  filled  with  water,  whereby  granulated  metal  is 
formed,  which  can  be  readily  reduced  in  a  mortar  to  a  fine 
powder.  This  powder  is  mixed  with  sal  ammoniac  and  gum- 
water  to  a  thin  paste.  This  paste  is  brought  into  the  designs 
produced  by  engraving  or  stamping  and  after  drying  burnt  in 
in  a  muffle.  When  cold  any  roughness  is  removed  by  grinding, 
and  after  polishing,  a  sharp  black  design  in  white  silver  is 
obtained. 

To  imitate  niel  by  electro-deposition  the  design  is  executed 
upon  the  surface  with  a  pigment  consisting  of  white  lead  and 
glue  or  gum-water.  The  portions  which  are  to  remain  free  are 
coated  with  "  stopping-off "  varnish,  and  the  design  is  uncovered 
by  etching  with  very  dilute  nitric  acid.  The  article  is  then 
brought  as  the  anode  into  dilute  solution  of  ammonium  sul- 
phide, while  a  small  sheet  of  platinum  connected  to  the  nega- 
tive pole  is  dipped  into  the  solution.  Sulphide  of  silver  being 
formed,  the  design  becomes  rapidly  black  gray,  and  after  re- 
moving the  "  stopping-off "  varnish  with  benzine,  stands  out  in 
sharp  contrast  from  the  white  silver. 

Upon  brass  nielling  may  be  imitated  by  silvering  the  article 
and  then  engraving  the  design,  by  which  the  silver  is  removed 
and  the  brass  uncovered.  The  article  is  then  brought  into  the 
black  bright  dip,  by  which  the  uncovered  brass  is  colored  black 
while  the  silvered  portions  remain  unchanged.  If  portions  in 
relief  are  to  be  made  black,  the  silvering  is  removed  by  grind- 
ing, the  article  dipped  into  cream  of  tartar  solution  and  then 
brought  into  the  black  bright  dip.  This  process  is  largely  em- 
ployed by  manufacturers  of  buttons  when  silvered  buttons  are 
to  be  supplied  with  the  name  of  the  firm  and  the  quality  number 
in  black. 

Old  (antique)  silvering. — To  give  silvered  articles  an  antique 
appearance,  coat  them  with  a  thin  paste  of  6  parts  graphite,  I 
red  ochre,  and  sufficient  spirits  of  turpentine.  After  drying,  a 
gentle  rubbing  with  a  soft  brush  removes  the  excess  of  powder, 
and  the  reliefs  are  set  off  (discharged)  by  means  of  a  rag 
dipped  into  alcohol. 


DEPOSITION    OF    SILVER.  283 

A  tone  resembling  antique  silvering  is  also  obtained  by  brush- 
ing the  silvered  articles  with  a  soft  brush  moistened  with  very 
dilute  alcoholic  solution  of  chloride  of  platinum. 

In  order  to  impart  the  old  silver  tinge  to  small  articles,  such 
as  buttons,  rings,  etc.,  they  are  agitated  in  the  above-mentioned 
paste,  and  then  "tumbled"  with  a  large  quantity  of  dry  sawdust 
until  the  desired  shade  is  obtained. 

Many  operators,  at  the  present  day,  produce  the  antique 
silvering  by  beginning  with  the  oxidizing  process  about  to  be 
described,  and  setting  off  the  reliefs  by  means  of  a  hard  brush 
and  pumice-stone,  or  Spanish  white.  This  last  process  is 
almost  exclusively  used  for  metallic  mountings  of  books  and 
albums. 

Oxidized  silver. — This  term  is  incorrect,  as  by  it  is  under- 
stood not  an  oxidation,  but  a  combination  with  sulphur  or 
chlorine.  Solution  of  pentasulphide  of  potassium  (liver  of 
sulphur  of  the  shops)  is  generally  used  for  the  purpose.  Im- 
merse the  articles  in  a  solution  of  2.75  drachms  of  liver  of 
sulphur  and  5^  drachms  of  ammonium  carbonate  in  I  quart 
of  water  heated  to  176°  F.,  and  allow  them  to  remain  until  they 
have  acquired  the  desired  dark  tone.  Immediately  after  im- 
mersion the  articles  become  pale  gray,  then  darker,  and,  finally, 
deep  black-blue.  For  coloring  in  this  manner  the  silvering 
should  not  be  too  thin  ;  for  articles  with  a  very  thick  deposit  of 
silver,  solution  of  double  the  strength  may  be  used.  Very 
slightly  silvered  articles  cannot  be  oxidized  in  this  manner,  as 
the  bath  would  remove  the  silvering,  or  under  the  most  favor- 
able circumstances  produce  only  a  gray  color.  If  the  operation 
is  not  successful,  and  the  articles  come  from  the  bath  stained 
or  otherwise  defective,  dip  them  in  a  warm  potassium  cyanide 
solution  which  rapidly  dissolves  the  silver  sulphide  formed. 

A  yellow  color  is  imparted  to  silvered  articles  by  immersion 
in  a  hot  concentrated  solution  of  chloride  of  copper,  rinsing  and 
drying. 

Stripping  silvered  articles. — When  a  silvering  operation  has 
failed,  or  the  silver  is  to  be  stripped  from  old  silvered  articles, 


284  ELECTRO-DEPOSITION    OF   METALS. 

different  methods  have  to  be  used  according  to  the  nature  of 
the  basis-metal.  Silvered  iron  articles  are  treated  as  the  anode 
in  potassium  cyanide  solution  in  water  (1:20),  the  iron  not 
being  brought  into  solution  by  potassium  cyanide.  As  cathode 
suspend  in  the  solution  a  few  silver  anodes  or  a  copper  sheet 
rubbed  with  an  oily  rag ;  the  silver  precipitates  upon  the  copper 
sheet,  but  does  not  adhere  to  it.  Articles,  the  basis  of  which  is 
copper,  are  best  stripped  by  immersion  in  a  mixture  of  equal 
parts  of  anhydrous  (fuming)  sulphuric  acid  and  nitric  acid  of 
40°  Be.  This  mixture  makes  the  copper  passive,  it  not  being 
attacked  while  the  silver  is  dissolved.  Care  must,  however,  be 
had  not  to  introduce  any  water  into  the  acids,  nor  to  let  them 
stand  without  being  hermetically  closed,  since  by  absorbing 
moisture  from  the  air  they  become  dilute  and  may  then  exert  a 
dissolving  effect  upon  the  copper.  The  fuming  sulphuric  acid 
may  also  be  heated  in  a  shallow  pan  of  enameled  cast-iron  to 
between  300°  and  400°  F.  Then  at  the  moment  of  using  it, 
pinches  of  dry  and  pulverized  nitrate  of  potassium  (saltpetre) 
are  thrown  into  it,  and  the  article,  held  with  copper  tongs,  is 
plunged  into  the  liquid.  The  silver  is  rapidly  removed,  while 
the  copper  or  its  alloys  is  but  slightly  corroded.  According 
to  the  rapidity  of  the  solution,  fresh  additions  of  saltpetre  are 
made.  All  the  silver  has  been  dissolved  when,  after  rinsing  in 
water  and  dipping  the  articles  into  the  cleansing  acids,  they  pre- 
sent no  brown  or  black  spots,  that  is  to  say,  when  they  behave 
like  new.  In  this  hot  acid  stripping  proceeds  more  quickly  than 
in  the  cold  acid  mixture,  but  the  latter  acts  more  uniformly. 

Determination  of  electro-deposited  silvering. — By  applying  to 
genuine  silvering,  a  drop  of  nitric  acid  of  1.2  specific  gravity,  in 
which  red  chromate  of  potash  has  been  dissolved  to  saturation, 
a  red  stain  of  chromate  of  silver  is  formed.  According  to 
Grager,  this  method  may  also  be  used,  to  a  certain  extent,  for 
the  recognition  of  other  white  metals  which  may  be  mistaken 
for  silver.  A  drop  of  the  mixture  applied  to  German  silver 
becomes  brown,  no  red  stain  appearing  after  rinsing  with  water ; 
upon  Britannia  the  drop  produces  a  black  stain ;  zinc  is  etched 


DEPOSITION    OF   SILVER.  285 

without  a  colored  spot  remaining  behind  ;  upon  amalgamated 
metals  a  brownish  precipitate  is  formed,  which  does  not  adhere 
and  is  washed  away  by  water;  upon  tin  the  drop  also  acquires 
a  brownish  color,  and  by  diluting  with  water  a  yellow  precipi- 
tate is  formed ;  upon  lead  a  beautiful  yellow  precipftate  is 
formed. 

Custom-house  officers  in  Germany  are  directed  by  law  to  use 
the  following  process  for  the  determination  of  genuine  silver- 
ing: Wash  a  place  on  the  article  with  ether  or  alcohol,  dry 
with  blotting  paper,  and  apply  to  the  spot  thus  cleansed  a  drop 
of  a  i  to  2  per  cent,  solution  of  crystallized  bisulphite  of  soda 
prepared  by  boiling  1.05  ozs.  of  sodium  sulphite  and  2.36 
drachms  of  flowers  of  sulphur  with  O.88  oz,  of  water  until  the 
sulphur  is  dissolved,  and  diluting  to  I  quart  of  fluid.  Allow 
the  drop  to  remain  upon  the  article  about  ten  minutes  and  then 
rinse  off  with  water.  Upon  silver  articles  a  full,  round,  steel- 
gray  spot  is  produced.  Other  white  metals  and  alloys,  with  the 
exception  of  amalgamated  copper,  do  not  show  this  phe- 
nomenon, there  appearing  at  the  utmost  a  dark  ring  at  the  edge 
of  the  drop.  Amalgamated  copper  is  more  quickly  colored 
and  acquires  a  more  dead-black  color  than  silver. 

Recovery  of  silver  from  old  silver  baths,  etc. — Old  solutions 
which  contain  silver  in  the  form  of  a  silver  salt  are  easily  treated. 
It  is  sufficient  to  add  to  them,  in  excess,  a  solution  of  common 
salt,  or  hydrochloric  acid,  when  all  the  silver  will  be  precipi- 
tated in  the  state  of  chloride  of  silver,  which,  after  washing,  may 
be  employed  for  the  preparation  of  new  baths. 

For  the  recovery  of  silver  from  solutions  which  contain  it  as 
cyanide,  the  solutions  may  be  evaporated  to  dryness,  the  residue 
mixed  with  a  small  quantity  of  calcined  soda  and  potassium 
cyanide,  and  fused  in  a  crucible,  whereby  metallic  silver  is 
formed,  which,  when  the  heat  is  sufficiently  increased,  will  be 
found  as  a  button  upon  the  bottom  of  the  crucible ;  or  if  it  is 
not  desirable  to  heat  to  the  melting-point  of  silver,  the  fritted 
mass  is  dissolved  in  hot  water,  and  the  solution  containing  the 
soda  and  cyanide  quickly  filtered  off  from  the  metallic  silver. 


286  ELECTRO-DEPOSITION    OF   METALS. 

The  evaporation  of  large  quantities  of  fluid,  to  be  sure,  is  in- 
convenient, and  requires  considerable  time.  But  the  reducing 
process  above  described  is  without  doubt  the  most  simple  and 
least  injurious. 

According  to  the  wet  method  the  bath  is  strongly  acidulated 
with  hydrochloric  acid,  provision  being  made  for  the  effectual 
carrying  off  of  the  hydrocyanic  acid  liberated.  Remove  the 
precipitated  chloride  of  silver  and  cyanide  of  copper  by  filtra- 
tion, and,  after  thorough  washing,  transfer  it  to  a  porcelain  dish 
and  treat  it,  with  the  aid  of  heat,  with  hot  hydrochloric  acid, 
which  will  dissolve  the  cyanide  of  copper.  The  resulting 
chloride  of  silver  is  then  reduced  to  the  metallic  state  by  mixing 
it  with  four  times  its  weight  of  crystallized  carbonate  of  soda 
and  half  its  weight  of  pulverized  charcoal.  The  whole  is  made 
into  a  homogeneous  paste,  which  is  thoroughly  dried,  and  then 
introduced  into  a  strongly  heated  crucible.  When  all  the 
material  has  been  introduced,  the  heat  is  raised  to  promote 
complete  fusion  and  to  facilitate  the  collection  of  the  separate 
globules  of  silver  into  a  single  button  at  the  bottom  of  the 
crucible,  where  it  will  be  found  after  cooling.  If  granulated 
silver  is  wanted,  pour  the  metal  in  a  thin  stream  and  from  a 
certain  height  into  a  large  volume  of  water. 

Still  simpler  is  the  reduction  of  the  chloride  of  silver  by  pure 
zinc ;  for  this  purpose  suspend  the  chloride  of  silver  in  water, 
add  hydrochloric  acid,  and  place  pure  zinc  rods  or  granulated 
zinc  in  the  fluid.  The  zinc  dissolving,  metallic  silver  is  sepa- 
rated, which  is  filtered  off,  washed,  and  dried. 

To  precipitate  the  silver  from  silver  solutions  containing 
potassium  cyanide  it  suffices  to  place  a  bright  sheet  of  zinc  in 
the  solution,  though  the  simultaneous  use  of  a  sheet  of  zinc  and 
a  sheet  of  iron  is  more  suitable.  While  with  the  use  of  zinc 
alone  the  silver  sometimes  adheres  firmly  to  the  zinc,  it  always 
separates  in  a  pulverulent  form  when  zinc  and  iron  are  em- 
ployed. It  is  only  necessary  to  wash  the  separated  silver, 
which,  as  a  rule,  contains  copper,  and  after  drying  to  dissolve 
it,  best  in  warm  concentrated  sulphuric  acid.  The  solution  is 


DEPOSITION    OF   GOLD.  287 

diluted  with  water  and  the  dissolved  silver  precipitated  by 
means  of  strips  of  copper.  The  silver  thus  obtained  is  perfectly 
pure.  If  the  content  of  copper  is  small,  it  may  be  removed 
from  the  silver  precipitated  with  zinc  by  fusing  with  a  small 
quantity  of  saltpetre  and  borax. 


CHAPTER  X. 

DEPOSITION   OF   GOLD. 

GOLD  is  chiefly  found  in  the  metallic  state,  and  generally 
alloyed  with  more  or  less  silver,  copper,  and  iron.  The  follow- 
ing analyses  will  serve  to  show  the  general  composition  of  the 
native  metal :  — 

Australia.  California.  Russia.  "Wales. 

Gold 94-64            89.10  98.96  89.83 

Silver 4.95             10.50  0.16  9.24 

Copper ....  0.05               

Iron 0.41               0.20  0.315              


IOC.GO  99.80  99-S2  99-°7 

Gold  is  one  of  the  few  metals  possessing  a  yellow  color ;  pre- 
cipitated from  its  solution  with  green  vitriol  or  oxalic  acid,  it 
appears  as  a  brown  powder  without  lustre,  which  on  pressing 
with  the  burnisher  acquires  the  color  and  lustre  of  fused  gold. 
Pure  gold  is  nearly  as  soft  as  lead,  but  possesses  considerable 
tenacity.  In  order  to  increase  its  hardness  when  used  for  arti- 
cles of  jewelry  and  for  coinage  it  is  mixed  with  silver  or  copper. 
The  "  fineness  of  gold,"  or  its  proportion  in  the  alloy,  is  usually 
expressed  by  stating  the  number  of  carats  present  in  24  carats 
of  the  mixture.  Pure  gold  is  stated  to  be  24  carats  '•  fine ;  " 
standard  gold  is  22  carats  "  fine ;  "  18  carat  gold  is  a  mixture  of 
18  parts  of  gold  and  6  of  alloy.  Gold  is  the  most  malleable  and 
ductile  of  the  metals ;  it  may  be  beaten  out  into  leaves  not  ex- 
ceeding roWoth  of  a  millimeter  in  thickness.  When  beaten 


288  ELECTRO-DEPOSITION    OF    METALS. 

out  into  thin  leaves  and  viewed  by  transmitted  light  gold  ap- 
pears green ;  when  very  finely  divided  it  is  dark  red  or  black. 
The  specific  gravity  of  fused  gold  is  19.35,  and  of  precipitated 
gold  powder  from  19.8  to  20.2.  Pure  gold  melts  at  about 
2016°  F.,  and  in  fusing  exhibits  a  sea-green  color.  The  melt- 
ing-points of  alloyed  gold  vary  according  to  the  degree  of  fine- 
ness. Thus,  23  carat  gold  melts  at  2012°  F. ;  22  carat  at' 
2009°;  20  carat  at  2002°;  18  carat  at  1995°;  15  carat  at 
1992°;  13  carat  at  1990°;  12  carat  at  1987°;  10  carat  at 
1982°;  9  carat  at  1979°;  8  carat  at  1973°;  7  carat  at  1960°. 
The  fineness  of  gold  may  be  approximately  estimated  by  means 
of  the  touch-stone,  a  balsatic  stone  formerly  obtained  from  Asia 
Minor,  but  now  procured  from  Saxony  and  Bohemia.  The 
sample  of  gold  to  be  tested  is  drawn  across  the  stone,  and  the 
streak  of  metal  is  treated  with  dilute  nitric  acid ;  from  the 
rapidity  of  the  action  and  the  intensity  of  the  green  color  pro- 
duced— due  to  the  solution  of  the  copper — as  compared  with 
streaks  made  by  alloys  of  known  composition,  the  assayer  is 
enabled  to  judge  of  the  proportion  of  inferior  metal  which  is 
present.  Gold  preserves  its  lustre  in  the  air  and  is  not  acted 
upon  by  any  of  the  ordinary  acids.  Nitric,  hydrocholoric,  or 
sulphuric  acid  by  itself  does  not  dissolve  gold,  but  it  dissolves 
in  acid  mixtures  which  develop  chlorine,  hence  in  aqua  regia 
(nitro-hydrochloric  acid). 

The  gold  found  in  commerce  under  the  name  of  shell-gold  or 
painter*  s  gold,  which  is  used  in  painting  and  for  repairing 
smaller  defects  in  electro-gilding,  is  prepared  by  triturating 
waste  in  the  manufacture  of  leaf  gold  with  water,  diluted  honey 
or  gum-water.  Gold  solution  may  also  be  precipitated  with 
antimonic  chloride.  The  resulting  precipitate  is  triturated  with 
barium  hydrate,  extracted  with  hydrochloric  acid,  and  after 
washing,  the  gold  powder  is  triturated  with  gum  arabic  solu- 
tion. 

Gold  baths. — Electro-gilding  may  be  done  with  the  aid  of 
heat  or  in  the  cold,  large  objects  being  generally  gilded  in  the 
cold  bath,  and  smaller  objects  in  the  hot  bath.  The  latter  has 


DEPOSITION    OF    GOLD.  289 

the  advantage  of  requiring  less  current-strength,  besides  yield- 
ing deposits  of  greater  density  and  uniformity  and  of  sadder, 
richer  tones.  Baths  for  hot  gilding  work  with  a  moderate  con- 
tent of  gold — 11^2  to  I2J^  grains  of  gold  per  quart — while 
baths  for  cold  gilding  should  contain  not  less  than  54  grains 
per  quart. 

'  Some  authors — for  instance,  Eisner,  Briant,  Selm,  and  others 
— give  the  preference  to  baths  prepared  with  potassium  ferro- 
cyanide ;  while  others,  like  Elkington  nnd  Regnault,  work  with 
a  solution  of  gold-salt  and  potassium  bicarbonate  ;  and  Bottcher, 
Leuchtenberg,  and  others  recommend  a  solution  of  cyanide  of 
gold  in  potassium  cyanide.  With  proper  treatment  of  the  bath, 
good  results  may  be  obtained  with  either.  However,  the  use 
of  baths  prepared  with  potassium  ferrocyanide  cannot  be  recom- 
mended on  account  of  the  secondary  decompositions  which 
take  place  during  the  operation  of  plating,  and  because  the 
baths  do  not  dissolve  the  gold  anodes.  In  the  following,  only 
approved  formulae  for  the  preparation  of  gold  baths  will  be 
given :  — 

I.  Bath  for  cold  gilding. — Fine  gold  in  the  form  of  fulmin- 
ating gold  54  grains,  98  per  cent,  potassium  cyanide  0.35  to 
0.5  oz.  (according  to  the  current-strength  used),  water  I  quart. 

To  prepare  this  bath,  dissolve  54  grains  of  fine  gold  in  aqua 
regia  in  a  porcelain  dish  heated  over  a  gas  or  alcohol  flame,  and 
evaporate  the  solution  to  dryness.  Continue  the  heating  until 
the  solution  is  thickly  fluid  and  dark  brown,  and  on  cooling 
congeals  to  a  dark  brown,  foliated  mass.  Heating  too  strongly 
should  be  avoided,  as  this  would  cause  decomposition  and  the 
auric  chloride  would  be  converted  into  aurous  chloride,  and 
eventually  into  metallic  gold  and  escaping  chlorine.  The 
neutral  chloride  of  gold  prepared  in  this  manner  is  dissolved  in 
i  pint  of  water  and  aqua  ammonia  added  to  the  solution  as 
long  as  a  yellow-brown  precipitate  is  formed,  avoiding,  how- 
ever, a  considerable  excess  of  aqua  ammonia.  The  precipitate 
of  fulminating  gold  is  filtered  off,  washed,  and  dissolved  in  I 
quart  of  water  containing  0.5  oz.  of  potassium  cyanide  in  solu- 
19 


2QO  ELECTRO-DEPOSITION    OF   METALS. 

tion.  The  solution  is  boiled,  replacing  the  water  lost  by 
evaporation,  until  the  odor  of  ammonia  which  is  liberated  by 
dissolving  the  fulminating  gold  in  potassium  cyanide  disappears 
when  it  is  filtered.  Instead  of  dissolving  the  gold  and  pre- 
paring neutral  chlorfde  of  gold  by  evaporating,  it  is  more  con- 
venient to  use  108  grains  of  chemically  pure  neutral  chloride  of 
gold  as  furnished  by  chemical  works,  and  precipitate  the  ful- 
minating gold  from  its  solution. 

Too  large  an  excess  of  potassium  cyanide  yields  gold  deposits 
of  an  ugly,  pale  color.  When  working  with  a  more  powerful 
current,  the  excess  of  potassium  cyanide  need  only  be  slight; 
with  a  weaker  current  it  must  be  larger.  With  10  per  cent, 
excess  of  free  potassium  cyanide,  the  most  suitable  current- 
strength  is  3  volts. 

The  fulminating  gold  should  not  be  dried,  as  in  this  condition 
it  is  highly  explosive,  but  should  be  immediately  dissolved 
while  in  a  moist  state. 

For  cold  gilding,  Roseleur  recommends  the  following  bath: 

II.  Fine   gold  as  neutral  chloride   of  gold  0.35   oz.,  98  per 
cent,  potassium  cyanide  0.7  oz.,  water  I  quart. 

Dissolve  the  gold-salt  from  0.35  oz.  of  fine  gold  or  about  0.7 
oz.  of  neutral  chloride  of  gold  in  y2  pint  of  water,  and  the  potas- 
sium cyanide  in  I  y2  pints  of  water,  and  after  mixing  the  solu- 
tions boil  for  half  an  hour,  The  preparation  of  this  bath  is 
more  simple  than  that  of  formula  I.,  but  the  color  of  the  gold 
deposit  obtained  with  the  latter  is  warmer  and  sadder  than  with 
the  first.  The  high  content  of  gold  in  the  bath,  prepared 
according  to  formula  II.,  readily  causes  a  red-brown  gold  de- 
posit, and  hence  special  attention  has  to  be  paid  to  the  regu- 
lation of  the  current. 

For  those  who  prefer  gold  baths  prepared  with  yellow  prus- 
siate  of  potash  instead  of  potassium  cyanide,  the  following 
formnla  for  cold  gilding  is  given:  — 

III.  Yellow  prussiate  of  potash  (potassium  ferrocyanide)  0.5 
oz.,  carbonate  of  soda  0.5  oz..  fine  gold  (as  chloride  of  gold  or 
fulminating  gold)  ~     75  grains,  water  I  quart. 


DEPOSITION   OF    GOLD.  2QI 

To  prepare  the  bath,  heat  the  solutions  of  the  yellow  prussiate 
of  potash  and  of  the  carbonate  of  soda  in  the  water  to  the  boil- 
ing-point, add  the  gold-salt,  and  boil  ^  hour,  or  with  the  use 
of  freshly  precipitated  fulminating  gold,  until  the  odor  of  am- 
monia disappears.  After  cooling,  the  solution  is  mixed  with  a 
quantity  of  distilled  water  corresponding  to  the  water  lost  by 
evaporation,  and  filtered.  This  bath  gives  a  beautiful  bright 
gilding  upon  all  metals,  even  upon  iron  and  steel.  Suitable 
current-strength  3.25  to  3.26  volts. 

Gold  bath  for  hot  gilding. — IV.  Fine  gold  (as  fulminating 
gold)  15.4  grains,  98  per  cent,  potassium  cyanide  77  grains, 
water  I  quart. 

This  bath  is  prepared  in  the  same  manner  as  that  according 
to  formula  I.,  from  15.4  grains  of  fine  gold,  which  is  converted 
into  neutral  chloride  of  gold  by  dissolving  in  aqua  regia  and 
evaporating;  or  dissolve  directly  29.32  to  30.75  grains  of 
chemically  pure  neutral  chloride  of  gold  in  water,  precipitate 
the  gold  as  fulminating  gold  with  aqua  ammonia,  wash  the  pre- 
cipitate, dissolve  it  in  water  containing  the  'potassium  cyanide, 
and  heat  until  the  odor  of  ammonia  disappears,  replacing  the 
water  lost  by  evaporation.  This  bath  yields  a  beautiful  sad 
gilding  of  great  warmth.  All  that  has  been  said  in  regard  to 
the  content  of  potassium  cyanide  in  the  bath  prepared  accord- 
ing to  formula  I.  also  applies  to  this  bath.  The  temperature 
should  be  between  158°  and  176°  F.,  and  the  current-strength 
2.0  to  2.5  volts. 

Roseleur  recommends  for  hot  gilding :  V.  Chemically  pure 
crystallized  sodium  phosphate  2.11  ozs.,  neutral  sodium  sul- 
phide 0.35  oz.,  potassium  cyanide  30.86  grains,  fine  gold  (as 
chloride)  15.43  grains,  distilled  water  I  quart. 

If  this  bath  is  to  serve  for  the  direct  gilding  of  steel,  only  [  5.43 
instead  of  30.86  grains  of  potassium  cyanide  are  to  be  used. 
Dissolve  in  a  porcelain  dish,  with  the  aid  of  moderate  heat,  the 
sodium  phosphate  and  sodium  sulphide,  and  when  the  solution 
is  cold,  add  the  neutral  chloride  of  gold  prepared  from  15.43 
grains  of  gold= about  30.86  grains  of  ci-  °Vnercial  chloride  of 


ELECTRO-DEPOSITION    OF   METALS. 

gold,  and  the   potassium    cyanide ;   for  use,  heat  the   bath   to 
between  158°  and  167°  F. 

Conrad  Taucher  recommends  the  following  formulae  for  hot 
gilding:  — 

VI.  Sodium  phosphate  14  ozs.,  sodium  bisulphite   3^  ozs., 
•sodium   bicarbonate   i  ^  ozs.,  caustic   potash   i^   ozs.,  potas- 
sium cyanide  14  drachms,  gold  in  the  form  of  neutral  chloride 
S^4  drachms,  distilled  water  10  quarts. 

With  the  exception  of  the  chloride  of  gold,  all  the  salts  may 
be  dissolved  together.  The  solution,  if  necessary,  is  filtered 
and  the  gold  solution  added.  The  bath  is  used  at  between  122° 
and  140°  F.  It  yields  a  very  beautiful  gilding,  but  requires  a 
quite  strong  current  for  its  decomposition.  It  is  not  suitable 
for  the  direct  gilding  of  steel. 

VII.  Yellow  prussiate  of  potash  (potassium  ferrocyanide)  5*^ 
ozs.,  pure  potassium  carbonate   i^  ozs.,  sal  ammoniac   11^ 
drachms,   gold   in  the  form  of  neutral  chloride  5^  drachms, 
water  5  quarts. 

Dissolve  with  the  assistance  of  heat  the  first  three  salts,  filter, 
and  when  cold  add  the  chloride  of  gold.  Then  heat  again  and 
boil  for  half  an  hour,  replacing  the  water  lost  by  evaporation. 

Many  electro-platers  prepare  the  gold  baths  with  the  assist- 
ance of  the  electric  current.  For  this  purpose  prepare  a  solu- 
tion of  3.52  ozs.  of  potassium  cyanide  (98  to  99  per  cent.)  per 
quart  of  water,  and  after  heating  to  between  122°  and  140°  F. 
conduct  the  current  of  two  Bunsen  elements  through  two  sheets 
of  gold,  not  too  small,  which  are  suspended  as  electrodes  in  the 
potassium  cyanide  solution.  The  action  of  the  current  is  inter- 
rupted when  the  solution  is  so  far  saturated  with  gold  that  an 
article  immersed  in  it  and  connected  to  the  negative  pole  in 
place  of  the  other  gold  sheet  is  gilded  with  a  beautiful  warm 
tone.  By  weighing  the  sheet  of  gold  serving  as  anode,  the 
amount  of  gold  which  has  passed  into  the  solution  is  ascer- 
tained. According  to  English  authorities,  a  good  gold  bath 
prepared  according  to  this  method  should  contain  3.52  ozs.  of 
potassium  cyanide  and  0.7  oz.  of  fine  gold  per  quart  of  water. 


DEPOSITION    OF    GOLD.  293 

The  only  advantage  of  this  mode  of  preparing  the  bath  is  that 
it  excludes  a  possible  loss  of  gold  which  may  occur  in  dissolv- 
ing gold,  evaporating  the  gold  solution,  etc.,  by  breaking  the 
vessel  containing  the  solution.  However,  by  using  commercial 
chemically  pure  chloride  of  gold  such  loss  is  avoided,  and  the 
bath  prepared  according  to  the  formulae  given  yields  richer 
tones  than  a  gold  bath  produced  by  electrolysis.  Besides,  the 
preparation  of  the  gold  bath  with  the  assistance  of  the  electric 
current  can  only  be  considered  for  smaller  baths,  since  the  sat- 
uration of  a  larger  .volume  of  potassium  cyanide  solution  re- 
quires considerable  time,  and  the  potassium  cyanide  is  strongly 
decomposed  by  long  heating. 

Management  of  gold  baths. — It  is  advisable  to  keep  the  con- 
tent of  gold  in  the  baths  prepared  according  to  the  different 
formulae  as  constant  as  possible,  which  is  best  effected  by  the 
use  of  fine  gold  anodes.  Insoluble  platinum  anodes  are  better 
liked  in  gilding  than  for  all  other  electro-plating  processes, 
partly  because  they  are  cheaper,  and  partly  because  they  are 
recommended  in  most  books  on  the  subject.  However,  a  bath 
which  has  become  low  in  gold  does  not  yield  a  beautiful  gold 
color,  and  has  to  be  frequently  strengthened  by  the  addition  of 
chloride  of  gold,  the  preparation  of  which  consumes  time  and 
causes  expense,  so  that  the  use  of  gold  anodes  is  the  cheapest 
in  the  end.  The  employment  of  anodes  of  platinum  strips  or 
platinum  wire  may,  perhaps,  be  advocated  for  coloring  the  de- 
posit, i.  e.j  for  the  purpose  of  obtaining  certain  tones  of  color 
when  gilding  in  the  hot  bath.  By  allowing  the  platinum  anode 
to  dip  only  slightly  in  the  bath  a  pale  gilding  is  obtained,  be- 
cause the  current  thereby  becomes  weaker ;  by  immersing  the 
anode  deeper  the  color  becomes  more  yellow,  and  by  immersing 
it  entirely  the  tone  becomes  more  reddish.  However,  instead 
of  producing  these  effects  of  the  current-strength  by  the  anode, 
which  requires  the  constant  presence  of  the  operator,  it  is  better 
to  obtain  the  coloration  by  means  of  the  resistance  board.  By 
placing  the  handle  upon  "  strong  "  a  reddish  gold  tone  is  ob- 
tained, and  by  placing  it  upon  "weak"  a  paler  gold  tone,  while 


294 


ELECTRO-DEPOSITION    OF   METALS. 


the  beautiful  gold  yellow  lies  in  the  middle  between  the  two  ex- 
tremes. However,  since  even  with  the  use  of  gold  anodes  the 
content  of  gold  in  the  bath  is  not  entirely  restored,  the  bath  has 
after  some  time  to  be  strengthened,  which  is  effected  by  a  solu- 
tion of  fulminating  gold  or  chloride  of  gold  in  potassium  cyan- 
ide, according  to  the  composition  of  the  bath. 

As  in  the  silvering  baths,  the  excess  of  potassium  cyanide  in 
the  gold  baths  is  also  partially  converted  into  potassium  carbo- 
nate by  the  action  of  the  air,  the  heat,  etc.,  and  it  is,  therefore, 
advisable  from  time  to  time  to  add  a  small  quantity  of  potas- 
sium cyanide. 

Gold  baths  for  cold  gilding  are  kept  in  vats  of  stoneware  or 
enameled  iron,  or  small  baths  in  glass  vats,  which,  to  protect 

FIG.  121. 


them  against  breaking,  are  placed  in  a  wooden  box.  Baths  for 
hot  gilding  require  enameled  iron  vats  in  which  they  can  be 
heated  by  a  direct  fire,  or  better,  by  placing  in  hot  water  (water 
bath),  or  by  steam.  For  small  gold  baths  for  hot  gilding,  a 
porcelain  dish  resting  upon  a  short-legged  iron  tripod  may  be 
used.  (Fig.  121.)  Beneath  the  iron  tripod  is  a  gas  burner 
supplied  with  gas  by  means  of  flexible  India-rubber  tubing  con- 
nected to  an  ordinary  gas  burner.  Across  the  porcelain  dish 


DEPOSITION    OF    GOLD.  295 

are  placed  two  glass  rods  around  which  the  pole-wires  are 
wrapped.  In  heating  larger  baths  in  enameled  vats  over  a 
direct  fire  it  may  happen  that  on  the  places  most  exposed  to 
the  heat  the  enamel  may  blister  and  peel  off;  it  is,  therefore, 
better  to  heat  the  baths  in  a  water  or  steam  bath.  For  this 
purpose  have  made  a  box  of  stout  iron  or  zinc  sheet  about 
^  inch  wider  and  longer,  and  about  4  inches  deeper  than  the 
enameled  vat  containing  the  gold  bath.  To  keep  the  level  of 
the  water  constant,  the  box  is  to  be  provided  with  a  water  inlet 
and  overflow  pipe.  In  this  box  place  the  vat  so  that  its  edges 
rest  upon  those  of  the  box,  and  make  the  joints  tight  with  tow. 
The  water-bath  is  then  heated  over  a  gas  flame  or  upon  a  hearth, 
the  water  lost  by  evaporation  being  constantly  replaced,  so  that 
the  enameled  vat  is  always  to  half  its  height  surrounded  by  hot 
water.  For  heating  by  steam  the  arrangement  is  the  same,  only 
a  valve  for  the  introduction  and  a  pipe  for  the  discharge  of 
steam  are  substituted  for  the  water  inlet  and  everflow  pipe. 

Execution  of  gilding. — Like  all  other  electro-plating  opera- 
tions, it  is  advisable  to  execute  gilding  with  an  external  source 
of  current;  that  is,  to  use  a  battery  or  other  source  of  current 
separated  from  the  bath,  and  to  couple  the  apparatuses  as  pre- 
viously described  and  illustrated  by  Figs.  52  and  54. 

To  be  sure,  there  are  still  gilders  who  gild  without  a  battery 
or  separate  external  source  of  current  and  obtain  good  results, 
the  process  being,  as  a  rule,  employed  only  in  gilding  small 
articles.  The  apparatus  used  for  this  purpose  consists  of  a  glass 
vessel  containing  the  gold  solution  compounded  with  a  large 
excess  of  potassium  cyanide  and  a  porous  clay  cell  filled  with 
very  dilute  sulphuric  acid  or  common  salt  solution,  which  is 
placed  in  the  glass  vessel ;  care  should  be  taken  to  have  the 
fluids  in  both  vessels  at  the  same  level.  Immerse  in  the  clay 
cell  an  amalgamated  zinc  cylinder  or  zinc  plate,  to  which  a 
copper  wire  is  soldered.  Outside  the  cell  this  copper  wire  is 
bent  downwards,  and  the  article  to  be  gilded,  which  dips  in  the 
gold  solution,  is  fastened  to  it.  In  working  with  this  apparatus 
there  is  always  a  loss  of  gold,  since  the  gold  solution  penetrates 


296  ELECTRO-DEPOSITION    OF   METALS. 

through  the  porous  cell,  and  on  coming  in  contact  with  the  zinc 
is  reduced  by  it,  the  gold  being  separated  as  black  powder  upon 
the  zinc.  In  cleaning  the  apparatus  this  black  slime  has  to  be 
carefully  collected  and  worked  for  fine  gold. 

For  the  sake  of  greater  solidity,  only  articles  of  silver  and 
copper  and  its  alloys  should  be  directly  gilded,  while  all  other 
metals  are  best  first  brassed  or  coppered.  Cleaning  from  grease 
and  pickling  is  done  in  the  same  manner,  as  described  on  page 
156.  The  preparation  of  the  articles  for  gilding  differs  from 
that  for  silvering  only  in  that  the  surfaces  which  later  on  are  to 
appear  with  high  lustre  are  not  artificially  roughened  with 
emery,  pumice,  or  by  pickling,  because,  on  the  one  hand,  the 
gold  deposit  seldom  needs  to  be  made  extravagantly  heavy, 
and  the  rough  surface  formed  would  require  more  laborious 
polishing  with  the  burnishers ;  and,  on  the  other,  the  gold  de- 
posits adhere  quite  well  to  highly- polished  surfaces,  provided 
the  current  strength  is  correctly  regulated,  and  the  bath  accu- 
rately composed  according  to  one  of  the  formulae  given.  Quick- 
ing  the  articles  before  gilding,  which  is  recommended  by  some 
authors,  is  not  necessary. 

The  current-strength  must,  under  no  circumstances,  be  so 
great  that  a  decomposition  of  water  and  consequent  evolution 
of  hydrogen  on  the  objects  take  place,  since  otherwise  the  gold 
would  not  deposit  in  a  reguline  and  coherent  form,  but  as  a 
brown  powder.  By  regulating  the  current  strength  so  that  it 
just  suffices  for  the  decomposition  of  the  bath,  and  avoiding  a 
considerable  surplus,  a  very  dense  and  uniform  deposit  is 
formed ;  and  by  allowing  the  object  to  remain  long  enough  in 
the  bath,  a  beautiful,  dull  gold  deposit  can  be  obtained  in  all 
the  baths  prepared  according  to  the  formulae  given.  It  may, 
however,  be  mentioned  that  this  mode  of  dull  gilding  is  the 
most  expensive,  since  it  requires  a  very  heavy  deposit,  and  it 
will,  therefore,  be  better  to  deaden  the  surface  previous  to  gild- 
ing according  to  a  process  to  be  described  later  on. 

For  gilding  with  cold  baths  two  freshly  filled  Bunsen  ele- 
ments coupled  for  tension  suffice  in  almost  all  cases,  while 


DEPOSITION   OF   GOLD.  297 

for  hot  baths  one  element  is,  as  a  rule,  sufficient,  if  the  anode 
surface  is  not  too  small.  The  more  electro- positive  the  metal 
to  be  gilded  is,  the  weaker  the  current  can  and  must  be. 

Though  gold  solutions  are  good  conductors  and,  therefore, 
the  portions  which  do  not  hang  directly  opposite  the  anodes 
gild  well,  for  the  solid  gilding  of  larger  objects  it  is  recom- 
mended to  frequently  change  their  positions  except  when  they 
are  entirely  surrounded  by  anodes. 

The  inner  surfaces  of  hollow-ware,  such  as  drinking-cups, 
milk  pitchers,  etc.,  are  best  gilded  after  freeing  them  from 
grease  and  pickling,  by  filling  the  vessel  with  the  gold  bath  and 
suspending  a  current-carrying  gold  anode  in  the  centre  of  the 
vessel,  while  the  outer  surface  of  the  latter  is  brought  in  con- 
tact with  the  negative  conducting  wire.  The  lips  of  vessels  are 
gilded  by  placing  upon  them  a  cloth  rag  saturated  with  the  gold 
bath  and  covering  the  rag  with  the  gold  anode. 

For  gilding  in  the  cold,  bath  the  process  is  as  follows :  The 
objects,  thoroughly  freed  from  grease  and  pickled  (and  if  of 
iron,  zinc,  tin,  Britannia,  etc.,  previously  coppered),  are  hung 
in  the  bath  by  copper  wires,  where  they  remain  with  a  weak 
current  until  in  about  8  or  10  minutes  they  appear  uniformly 
gilded.  At  this  stage  they  are  taken  from  the  bath,  rinsed  in  a 
pot  filled  with  water,  which,  after  working  for  some  time,  is 
added  to  the  bath  to  replace  the  water  lost  by  evaporation,  and 
brushed  with  a  fine  brass  scratch-brush  and  tartar  solution. 
They  are  then  thoroughly  rinsed,  again  freed  from  grease  by 
brushing  with  lime-paste  and  then  returned  to  the  bath,  where 
they  remain  until  they  have  acquired  a  deposit  of  sufficient 
thickness. 

If  it  is  intended  to  give  them  a  very  heavy  deposit,  it  is  advis- 
able to  scratch-brush  them  several  times  with  the  use  of  tartar 
or  its  solution.  For  gilding  by  weight  the  same  plan  as  given 
for  silvering  (p.  260)  is  pursued. 

For  gilding  with  the  hot  bath  the  operations  are  the  same, 
with  the  exception  that  a  weaker  current  is  introdued  into  the 
bath  and  the  time  of  the  gilding  process  shortened.  Frequent 


298  ELECTRO-DEPOSITION    OF   METALS. 

scratch-brushing  also  increases  the  solidity  of  the  deposit  and 
prevents  the  premature  turning  to  a  dead  brown-black.  Since 
in  hot  gilding  more  gold  than  intended  is  readily  deposited,  it 
is  especially  advisable  to  place  a  resistance  board  in  the  circuit, 
as  otherwise  the  operator  must  remain  standing  alongside  of  the 
bath  and  regulate  the  effect  of  the  current  by  immersing  the 
anodes  more  or  less. 

With  a  somewhat  considerable  excess  of  potassium  cyanide, 
and  if  the  objects  to  be  gilded  are  not  rapidly  brought  in  con- 
tact with  the  current-carrying  object  rod,  hot  gold  baths  cause 
the  solution  of  some  metal.  Therefore,  when  silver  or  silvered 
objects  are  constantly  gilded  in  them  they  yield  a  somewhat 
greenish  gilding  in  consequence  of  the  absorption  of  silver,  or 
a  reddish  gilding  due  to  the  absorption  of  copper,  if  copper  or 
coppered  articles  are  constantly  gilded  in  them.  Hence,  for 
the  production  of  such  green  or  reddish  color,  gilding  baths 
which  have  thus  become  argentiferous  or  cupriferous  may  be 
advantageously  used.  In  order  to  obtain  a  deposit  of  green  or 
red  gold  with  fresh  baths,  the  tone-giving  addition  of  metal  must 
be  artificially  effected,  as  will  immediately  be  seen. 

If,  however,  such  extreme  tones  are  not  desired,  the  content 
of  gold  in  the  baths  may  be  exhausted  for  preliminary  gilding 
with  the  use  of  platinum  anodes,  the  sad  gold  color  being  then 
given  in  a  freshly  prepared  bath. 

The  gold  deposits  are  polished,  in  the  same  manner  as  silver 
deposits,  with  the  burnisher  and  red  ochre,  and  moistening  with 
solution  of  soap,  decoction  of  flaxseed,  or  soap-root,  etc. 

Red  gilding. — In  order  to  obtain  a  red  gold  with  the  formulae 
given,  a  certain  addition  of  cyanide  of  copper  dissolved  in  potas- 
sium cyanide  has  to  be  made  to  them.  The  quantity  of  such 
addition  cannot  be  well  expressed  by  figures,  since  the  current- 
strength  with  which  the  articles  are  gilded  exerts  considerable 
influence.  It  is  best  to  triturate  the  cyanide  of  copper  in  a 
mortar,  to  a  paste  with  water,  and  add  of  this  paste  to  a  mode- 
rately concentrated  potassium  cyanide  solution  as  long  as 
cyanide  of  copper  is  dissolved.  Of  this  copper  solution  add, 


DEPOSITION    OF   GOLD.  299 

gradually  and  in  not  too  large  portions,  to  the  gold  solution 
until,  with  the  current-strength  used,  the  gold  deposit  shows 
the  desired  red  tone.  The  absorption  of  copper  by  the  bath 
may  also  be  effected  by  replacing  the  gold  anodes  by  copper 
anodes  and  circulating  the  current  (suspending  a  few  gold 
anodes  to  the  object  rod).  The  direct  addition  of  cyanide  of- 
copper  is,  however,  preferable. 

For  the  determination  of  the  content  of  copper  required  for 
the  purpose  of  obtaining  a  beautiful  red  gold,  a  bath  for  hot 
gilding  which  contained  10.8  grains  of  gold  per  quart  was  com- 
pounded with  a  solution  of  cyanide  of  copper  in  potassium 
cyanide  with  1 .08  grains  content  of  copper.  The  tone  of  the 
gilding,  which  previously  was  pure  yellow,  immediately  passed 
into  a  pale  red  gold.  By  the  further  addition  of  1.08  grains  of 
copper  a  fiery  red  gold  tone  was  obtained,  while  a  third  addi- 
tion of  1. 08  grains  of  copper  yielded  a  color  more  approach- 
ing that  of  copper  than  of  gold.  These  experiments  show 
that  20  per  cent,  of  copper  of  the  weight  of  gold  contained  in 
the  bath  seems  to  be  the  most  suitable  proportion  for  obtain- 
ing a  beautiful  red  gold. 

Green  gilding. — To  obtain  a  greenish  gilding,  solution  of 
cyanide  or  chloride  of  silver  in  potassium  cyanide  has  to  be 
added  to  the  gold  bath.  It  is  not  easy  to  prepare  greenish 
gilding  of  a  pleasing  color,  and  to  obtain  it  the  current-strength 
must  be  accurately  proportioned  to  the  object-surface,  since 
with  too  weak  a  current  silver  predominates  in  the  deposit,  the 
gilding  then  turning  out  whitish,  while  too  strong  a  current  de- 
posits too  much  gold  in  proportion  to  silver,  the  gilding 
becoming  yellow,  but  not  green. 

Rose-color  gilding  may  be  obtained  by  the  addition  of  suit- 
able quantities  of  copper  and  silver  solution,  but  such  colora- 
tion requires  much  attention  and  thought. 

Dead  gilding. — As  previously  mentioned,  a  beautiful  dead 
gold  deposit  may  be  obtained  by  the  use  of  any  of  the 
formulae  given  and  a  correctly  regulated  current,  and  allowing 
sufficient  length  of  time  for  gilding ;  but  the  heavy  deposit  of 


300  ELECTRO-DEPOSITION    OF   METALS. 

gold  required  for  this  process  makes  it  too  expensive,  and  it  is 
therefore  advisable  to  produce  dead  gilding  without  excessively 
heavy  deposits  by  previous  deadening  of  the  basis-surface. 
The  process  of  graining  has  already  been  described  on  p.  277  ; 
another  method  is  to  deaden  the  first  thin  deposit  of  gold  with 
the  deadening  scratch-brush,  and  then  to  give  a  second  deposit 
of  gold,  which  also  turns  out  dead  upon  the  deadened  surface. 
However,  this  operation  of  deadening  with  the  scratch-brush 
requires  considerable  skill,  and  it  is  therefore  best  to  deaden 
the  surface  according  to  one  of  the  following  methods:  — 

For  this  purpose,  the  mixture  of  I  volume  of  saturated  solu- 
tion of  bichromate  of  potash,  and  2  volumes  of  concentrated 
hydrochloric  acid,  mentioned  on  p.  156,  may  be  used.  Brass 
articles  are  allowed  to  remain  in  the  mixture  several  hours, 
and  are  then  quickly  drawn  through  the  bright-dipping  bath ; 

Or,  by  depositing  upon  the  articles  a  coating  of  frosted  silver 
and  then  gilding  in  a  good  gold  bath.  Unfortunately,  this 
method  is  somewhat  expensive,  and  the  burnished  parts  are 
greenish.  Moreover,  the  intermediary  coat  of  silver  is  easily 
affected  by  sulphurous  gases,  the  gilding  being  thereby 
blackened. 

More  advantageous  is  the  process  of  providing  the  articles 
with  a  dead  copper  coating  in  the  acid  galvanoplastic  copper 
bath,  then  quicking  them,  and  finally  gilding.  This  gilding  is 
very  handsome  in  lustre  and  color. 

Dead  gilding  on  zinc. — By  the  following  process  of  deposit- 
ing gold  on  zinc,  effects  similar  to  those  of  fire-gilding  on  bronze 
are  produced.  The  zinc  is  first  heavily  coppered  in  one  of  the 
copper  baths  previously  given,  and  is  then  brought  into  a  silver- 
ing bath  (with  use  of  a  battery)  or  into  an  acid  copper  bath 
(see  "  Galvanoplasty  "),  according  to  whether  deadening  is  to 
be  effected  with  silver  or  copper.  In  deadening  in  the  acid 
copper  bath  care  should  be  taken  that  the  suspending  wires  are 
in  contact  with  the  object-rod  before  immersing  the  coppered 
zinc  object  in  the  bath.  However,  this  process  of  coppering 
zinc  in  the  acid  copper  bath  is  a  very  delicate  operation,  it  being 


DEPOSITION    OF    GOLD.  3OI 

requently  observed  that  even  with  an  apparently  very  heavy 
coppering  in  the  electro-coppering  bath,  brownish-black  spots 
appear  on  the  objects  when  brought  into  the  acid  bath,  the 
copper  being  deposited  on  these  spots  in  a  pulverulent  form  by 
the  contact  of  the  acid  bath  with  the  zinc.  If  this  is  observed, 
the  objects  have  to  be  immediately  taken  from  the  bath,  and 
after  thorough  scratch-brushing  again  thoroughly  and  quickly 
coppered  in  the  electro-coppering  bath  before  returning  them  to 
the  acid  copper  bath.  It  may  be  recommended,  first  to  provide 
the  coppered  zinc  objects  with  a  thin  coat  of  nickel,  and  then 
to  copper  them  in  the  acid  copper  bath. 

When  the  deposit  seems  of  sufficient  thickness,  the  zinc  is 
washed  in  a  large  quantity  of  water,  drawn  through  a  weak 
solution  of  mercurous  nitrate,  and  brought  into  a  hot  gilding 
bath  composed  as  follows:  Water  10  quarts,  sodium  phosphate 
21  ozs.,  sodium  bisulphite  3^  ozs.,  potassium  cyanide  iij{ 
drachms,  gold  (in  the  form  of  chloride)  5^  drachms. 

At  first  quite  a  strong  current  is  used,  which  is  gradually  re- 
duced up  to  the  moment  when  the  object  is  taken  from  the  bath. 

Coloring  of  the  gilding. — It  has  been  frequently  mentioned 
that  the  most  rational  and  simple  process  of  giving  certain 
tones  of  color  to  the  gilding  is  by  means  of  a  stronger  or  weaker 
current.  Many  operators,  however,  cling  to  the  old  method  of 
effecting  the  coloration  by  gilder's  wax  or  brushing  with  certain 
mixtures,  and  for  this  reason  this  process,  which  is  generally 
used  for  coloring  fire-gilding,  shall  be  briefly  mentioned. 

To  impart  to  the  gold-deposit  a  redder  color,  the  gilding-wax 
is  prepared  with  a  greater  content  of  copper,  while  for  greenish 
gilding  more  zinc-salt  is  added.  There  are  innumerable  re- 
ceipts for  the  preparation  of  gilding-wax,  nearly  every  gilder 
having  his  own  receipt,  which  he  considers  superior  to  all 
others.  Only  two  formulae  which  yield  good  results  will  here 
be  given,  one  (I.)  for  reddish  gilding  and  one  (II.)  for  greenish 
gilding. 

I.  Wax  12  parts  by  weight,  pulverized  verdigris  8,  pulver- 
ized sulphate  of  zinc  4,  copper  scales  4,  borax  I,  pulverized 
bloodstone  6,  copperas  2. 


302  ELECTRO-DEPOSITION    OF   METALS. 

II.  Wax  12  parts  by  weight,  pulverized  verdigris  4,  pulver- 
ized sulphate  of  zinc  8,  copper  scales  2,  borax  I,  pulverized 
bloodstone  6,  copperas  2. 

Gilder's  wax  is  prepared  as  follows:  Melt  the  wax  in  an  iron 
kettle,  add  to  the  melted  mass,  with  constant  stirring,  the  other 
ingredients,  pulverized  and  intimately  mixed,  in  small  portions, 
and  stir  until  cold,  so  that  the  powder  cannot  settle  on  the 
bottom  or  form  lumps.  Finally,  mould  the  soft  mass  into 
sticks  about  %  inch  in  diameter. 

The  operation  for  applying  the  gilder's  wax  is  as  follows : 
Coat  the  heated  gilded  articles  uniformly  with  the  wax  and 
burn  off  over  a  charcoal  fire,  frequently  turning  the  articles. 
After  the  extinguishment  of  the  wax  flames,  plunge  the  articles 
into  water,  scratch-brush  with  wine-vinegar,  dry  in  sawdust, 
and  polish.  , 

To  give  gilded  articles  a  beautiful,  rich  appearance,  the  fol- 
lowing process  may  also  be  used :  Mix  3  parts  by  weight  of 
pulverized  alum,  6  of  saltpetre,  3  of  sulphate  of  zinc,  and  3  of 
common  salt,  with  sufficient  water  to  form  a  thinly-fluid  paste. 
Apply  this  paste  as  uniformly  as  possible  to  the  articles  by 
means  of  a  brush,  and  after  drying,  heat  the  coating  upon  an 
iron  plate  until  it  turns  black ;  then  wash  in  water,  scratch- 
brush  with  wine-vinegar,  dry,  and  polish. 

According  to  a  French  receipt^  the  same  result  is  attained  by 
mixing  pulverized  blue  vitriol  3  parts  by  weight,  verdigris  7, 
sal  ammoniac  6,  and  saltpetre  6,  with  acetic  acid  31  ;  immers- 
ing the  gilded  articles  in  the  mixture  or  applying  the  latter 
with  a  brush ;  then  heating  the  objects  upon  a  hot  iron  plate 
until  they  turn  black,  and,  after  cooling,  pickling  in  concen- 
trated sulphuric  acid. 

Some  gilders  improve  bad  tones  of  gilding  by  immersing  the 
articles  in  dilute  solution  of  nitrate  of  mercury  until  the  gilding 
appears  white ;  the  mercury  is  then  evaporated  over  a  flame 
and  the  articles  are  scratch-brushed.  Others  apply  a  paste  of 
pulverized  borax  and  water,  heat  until  the  borax  melts,  and 
then  quickly  immerse  in  dilute  sulphurfc  acid. 


DEPOSITION    OF    GOLD. 


303 


Incrustations  with  gold  are  produced  in  the  same  manner  as 
incrustations  with  silver  described  on  p.  281. 

Gilding  of  metallic  wire  and  gauze, — Fine  wire  of  gilded 
copper  and  brass  is  much  used  in  the  manufacture  of  metallic 
fringes  and  lace,  for  epaulettes  and  other  purposes.  The  fine 
copper  and  brass  wires  being  drawn  through  the  draw-irons 
and  wound  upon  spools  by  special  machines,  and  hence  not 
touched  by  the  hands,  freeing  from  grease  may,  as  a  rule,  be 
omitted.  The  first  requisite  for  gilding  is  a  good  winding 
machine,  which  draws  the  wires  through  the  gold  bath  and 

FIG.  122. 


wash  boxes,  and  further  effects  the  winding  of  the  wire  upon 
spools.  The  principal  demand  made  in  the  construction  of 
such  a  machine  is  that  by  means  of  a  simple  manipulation  a 
great  variation  in  the  speed  with  which  the  wire  or  gauze 
passes  through  the  gold  bath  can  be  obtained.  This  is  neces- 
sary in  order  to  be  able  to  regulate  the  thickness  of  the  gild- 
ing by  the  quicker  or  slower  passage  of  the  wire.  A  machine 
well  adapted  for  this  purpose  is  that  constructed  by  J.  W. 
Spaeth  and  shown  in  Fig.  122. 


304  ELECTRO-DEPOSITION   OF   METALS. 

The  variation  in  the  passage  of  the  wire  is  attained  by  the 
two  friction-pulleys  F,  which  sit  upon  a  common  shaft  with 
the  driving-pulley,  R,  and  transmit  their  velocity  by  means 
of  the  friction-pistons  KK1  to  the  friction-pulley  Ft  which  is 
firmly  connected  to  the  belt-pulley  R  driving  the  spool  spindle. 
Since  by  a  simple  device  the  pistons  K  and  K'  may  be  shifted, 
it  is  clear  that  the  transmission  of  the  number  of  revolutions 
from  F  \.o  F  is  dependent  on  the  position  of  the  friction  pistons 
K  and  K' ',  and  that  the  velocity  will  be  the  greater  the  shorter 
the  distance  they  are  from  the  centre  of  friction-pulleys  F  and  F. 
In  order  that  the  friction  between  F,  K,  and  F  may  always  be 
sufficient  for  the  transmission  of  the  motion,  even  when  the 
pistons  are  worn,  four  weights,  G,  are  provided,  which  press  the 
above-mentioned  parts  firmly  against  each  other. 

In  front  of  each  spool  of  this  machine  is  inserted  a  small 
enameled  iron  vat  which  contains  the  gold  bath,  and  is  heated 
by  a  gas  flame  to  about  167°  F.  Between  this  bath  and  the 
winding  machine  is  another  small  vat  with  hot  water  in  which 
the  gilded  wire  is  rinsed. 

The  wires  unwind  from  a  reel  placed  in  front  of  the  gold 
baths,  run  over  a  brass  drum  which  is  connected  to  the  negative 

FIG.  123. 


pole  of  the  source  of  current,  and  transmits  the  current  to  the 
wires ;  the  dipping  of  the  wires  into  the  gold  bath  is  effected 
by  porcelain  drums,  which  are  secured  to  heavy  pieces  of  lead 
placed  across  the  vats  as  shown  in  Fig.  123.  The  gilded  wire 
being  wound  upon  the  spools  of  the  winding  machine,  these 
spools  are  removed  and  thoroughly  dried  in  the  drying  cham- 
ber. The  wire  is  then  again  reeled  off  on  to  a  simple  reel,  in 
•doing  which  it  is  best  to  pass  it  through  between  two  soft 
pieces  of  leather  to  increase  its  lustre. 


DEPOSITION    OF    GOLD.  305 

The  most  suitable  gold  bath  is  that  prepared  according  to 
formula  IV. ;  the  current-strength  should  be  from  6  to  8  volts, 
which  will  produce  a  deposit  of  sufficient  thickness  even  with 
the  wire  passing  at  the  most  rapid  rate  through  the  bath. 

Gilding  by  contact,  by  immersion,  and  by  friction. — For  contact 
gilding  by  touching  with  zinc,  formulae  I.,  II.,  IV.,  and  V.,  may 
be  used,  IV.  and  V.  being  especially  suitable  if  the  addition  of 
potassium  cyanide  is  somewhat  increased  and  the  baths  are 
sufficiently  heated. 

A  contact  gold  bath  prepared  with  yellow  prussiate  of  potash 
according  to  the  following  formula  also  yields  a  good  deposit: 

VIII.  Fine  gold  as  chloride  of  gold  54  grains,  yellow  prussiate 
of  potash  I  oz.,  potash  I  oz.,  common  salt  I  oz.,  water  I  quart. 
The  bath  is  prepared  as  given  for  formula  III. ;  for  use,  heat  it 
to  boiling. 

Gilding  by  contact  is  done  the  same  way  as  silvering  by  con- 
tact. The  points  of  contact  must  be  frequently  changed,  since 
in  the  gold  bath  intense  stains  are  still  more  readily  formed  than 
in  the  silver  bath. 

For  gilding  by  contact,  Conrad  Taucher  recommends  the  fol- 
lowing bath :  Distilled  water  10  quarts,  sodium  or  potassium 
pyrophosphate  28  ozs.,  prussic  acid  4^  drachms,  crystallized 
chloride  of  gold  13  j£  drachms. 

To  prepare  the  bath,  bring  into  a  porcelain  vessel  or  into  a 
dish  of  enameled  cast-iron  9  quarts  of  distilled*  water  and  add 
the  28  ozs.  of  pyrophosphate,  stirring  constantly  with  a  glass 
rod.  Then  heat,  and  when  solution  is  complete  filter  and  set 
aside  to  cool. 

While  filtering  the  solution,  the  chloride  of  gold  is  prepared 
by  bringing  into  a  small  glass  flask  5  j£  drachms  of  fine  rolled 
gold,  14  drachms  of  pure  hydrochloric  acid,  and  Sy^  drachms 
of  pure  nitric  acid.  Apply  a  gentle  heat  to  the  bottom  of  the 
flask.  In  a  few  seconds  vigorous  effervescence  accompanied 

*  The  use  of  distilled  water  is  necessary,  otherwise  the  lime  salts  contained   in 
ordinary  water  would  decompose  a  portion  of  the  pyrophosphate. 
20 


306  ELECTRO-DEPOSITION    OF   METALS. 

by  the  evolution  of  orange-red  vapors  takes  place,  and  the  gold 
in  a  few  minutes  dissolves  to  a  reddish-yellow  fluid.  To  evapo- 
rate an  excess  of  acids,  which  if  brought  into  the  bath  might 
cause  serious  disturbances  and  even  render  the  bath  entirely 
useless,  the  flask  is  placed  upon  a~piece  of  sheet-iron  provided 
in  the  centre  with  a  hole  about  o.n  inch  in  diameter,  and 
heated  upon  a  stove  or  over  a  spirit  lamp.  When  no  more 
vapors  escape  and  the  solution  has  become  thickly-fluid  and 
has  acquired  an  intense  hyacinth-red  color,  remove  the  flask 
from  the  fire  by  means  of  wooden  pincers  and  let  cool.  If  prop- 
erly prepared,  the  chloride  of  gold  then  congeals  to  an  aggre- 
gate of  saffron-yellow  acicular  crystals.  If  the  color  of  the 
latter  is  red,  too  much  heat  has  been  applied.  Such  chloride 
of  gold  is  very  suitable  for  the  preparation  of  electro-gilding 
baths,  but  if  it  is  to  be  used  for  contact  gilding  a  small  quantity 
of  the  above-mentioned  two  acids  has  to  be  added,  and,  after 
heating,  the  mass  has  to  be  again  evaporated. 

It  frequently  happens  that  by  careless  manipulation  the  gold 
is  "burnt,"  i.  e.,  the  auric  chloride  is  decomposed  by  too  long, 
continued  heating  and  is  converted  into  insoluble  aurous 
chloride,  or  even  into  pulverulent  metallic  gold.  If  such  is  the 
case,  the  treatment  with  the  above-mentioned  mixture  of  acids 
has  to  be  repeated.  The  object  of  the  perforated  piece  of 
sheet- iron  on  which  the  flask  is  placed  for  the  purpose  of 
evaporating  the  solution  is  to  prevent  the  sides  of  the  flask 
from  being  heated  too  strongly,  as  otherwise  the  thin  layers  of 
chloride  of  gold  solution  might  be  decomposed. 

In  practice  porcelain  capsules  which  are  heated  in  a  sand 
bath  are  generally  used  for  dissolving  gold.  Fig.  124  shows 
such  a  capsule  with  glass  funnel  in  a  sand  bath  over  a  gas 
stove.  The  purpose  of  the  glass  funnel  is  to  prevent  any  fluid 
from  being  thrown  from  the  capsule  at  the  moment  of  the  effer- 
vescence caused  by  the  action  of  the  acids  upon  the  metal. 

The  cold  crystallized  chloride  of  gold  in  the  flask  or  the  cap- 
sule is  now  dissolved  in  a  small  quantity  of  distilled  water, 
solution  being  effected  almost  immediately.  The  solution  is 


DEPOSITION    OF    GOLD.  3O/ 

poured  upon  a  filter  of  filtering  paper  in  a  glass  funnel  placed 
upon  a  clean  bottle.  A  small  piece  of  paper  should  be  inserted 
between  the  funnel  and  the  neck  of  the  bottle,  so  that  the  air 
can  escape  from  the  latter  and  the  fluid  run  off  from  the  filter. 

FIG.  124. 


The  object  of  filtering  is  to  separate  the  small  quantity  of 
chloride  of  silver  formed  from  the  little  silver  which  is  present 
even  in  the  purest  commercial  gold.  To  bring  all  the  gold  into 
the  bath,  repeatedly  wash  the  bottle  and  the  filter  with  a  small 
quantity  of  distilled  water. 

Now  mix  the  cold  solution  of  the  pyrophosphate  and  that  of 
the  chloride  of  gold  by  pouring  the  latter  graeually  into  the 
former  and  stirring  with  a  glass  rod.  Then  add  the  4^  drachms 
of  prussic  acid  and  heat  to  the  boiling  point,  when  the  bath  is 
ready  for  use. 

When  mixed  cold  the  bath  has  a  yellow  or  yellow-greenish 
color,  which  disappears  as  the  temperature  rises.  However,  the 
fluid  sometimes  becomes  currant-red  or  violet,  which  indicates 
that  it  contains  too  little  prussic  acid.  This  is  remedied  by 
adding  drop  by  drop  prussic  acid  until  the  fluid  is  entirely  dis- 
colored. Great  care  must,  however,  be  exercised  in  adding  the 
acid,  as  on  excess  of  it  renders  the  gilding  pale. 

By  following  the  directions  above  given,  the  bath  is  very  suit- 


308  ELECTRO-DEPOSITION    OF   METALS. 

able  for  producing  a  beautiful  yellow  gilding  on  objects  previ- 
ously thoroughly  cleansed.  The  articles  should  be  passed 
through  a  very  weak  solution  of  mercurous  nitrate,  otherwise 
the  gilding  shades  and  becomes  reddish.  The  articles  to  be 
gilded  must  be  constantly  moved  in  the  bath  ;  they  are  sus- 
pended to  hooks  or  brought  into  the  bath  in  dipping  baskets  of 
stoneware  or  brass. 

Gilding  is  finished  in  a  few  seconds.  The  articles  are  then 
washed  in  clean  water,  dried  in  dry  and  warm  sawdust,  and  if 
necessary,  immediately  polished. 

By  neglecting  the  precautionary  measures  given  above,  the 
gilding  sometimes  appears  tarnished  and  dissimilar  in  tone  It 
is  then  colored  or  treated  with  the  so-called  matt  for  gilded 
articles. 

For  this  purpose  melt  equal  parts  of  the  following  salts  in 
their  water  of  crystalization  at  about  212°  F. :  Ferrous  sulphate 
(green  vitriol),  zinc  sulphate  (white  vitriol),  alum,  and  salt- 
petre. 

Thoroughly  wet  every  portion  of  the  defective  gilding  by  turn- 
ing the  articles  about  in  this  mixture.  Then  place  them  in  the 
centre  of  a  cylindrical  stove,  in  which  the  coal  burns  between 
the  sides  and  a  cylindrical  grate,  so  that  the  entire  heat  radiates 
toward  the  empty  space  in  the  centre.  The  salts  melt  and  then 
get  into  a  fiery  flux,  the  entire  mass  acquiring  a  dull  earthen 
color.  When  on  touching  the  articles  with  the  moistened 
finger  a  slight  hissing  noise  is  heard,  the  temperature  is  suffi- 
ciently high  and  the  articles  are  thrown  into  weak  starch-water 
acidulated  with  sulphuric  acid.  The  coating  of  salts  dissolves 
immediately  and  the  gilding  presents  a  beautiful  warm  and  uni- 
form appearance.  This  operation  can,  of  course,  only  be  exe- 
cuted if  the  entire  article  has  been  gilded. 

Baths  for  gilding  by  dipping.  The  following  two  formulas 
have  stood  the  test : 

I.  Crystalized  sodium  pyrophosphate  2.82  ozs.,  12  per  cent, 
prussic  acid  4.51  drachms,  crystalized  chloride  of  gold  1.12 
drachms,  water  I  quart.  Heat  the  bath  to  the  boiling  point, 


DEPOSITION   OF   GOLD.  309 

and  immerse  the  pickled  objects  of  copper  or  its  alloys,  mov- 
ing them  constantly  until  gilded.  Iron,  steel,  tin,  and  zinc 
should  be  previously  coppered,  coating  the  objects  with  mercury 
(quicking)  being  entirely  superfluous. 

All  gold  baths  prepared  with  sodium  pyrophosphate,  when 
fresh,  give  rapid  and  beautiful  results,  but  they  have  the  dis- 
advantage of  rapidly  decomposing,  and  consequently  can  seldom 
be  completely  exhausted.  In  this  respect  the  following  formula 
answers  much  better : 

II.  Crystalized    sodium  phosphate  2.82   drachms,  chemically 
pure    caustic    potash    1.69    drachms,    chloride    of    gold    0.56 
drachm,  98  per  cent,  potassium  cyanide  9.03  drachms,  water  I 
quart.     Dissolve  the  sodium   phosphate  and  caustic  potash  in 
y^   of  the  water,  and  the  potassium  cyanide  and  chloride  of 
gold  in  the  remaining  ^,  and  mix  both   solutions.     Heat  the 
solution  to  the  boiling  point.     This  bath  can  be  almost  entirely 
exhausted,  it  not  being  decomposed  by  keeping.     Should  the 
bath    become    weak,  add    about    2^    drachms    of    potassium 
cyanide,  and  use  it  for  preliminary  dipping  until  no  more  gold 
is  reduced.     To  complete  gilding,  the  objects  subjected  to  such 
preliminary  dipping  are  then  immersed  for  a  few  seconds  in  a 
freshly-prepared  bath  of  the  composition  given  above. 

The  layer  of  gold  formed  is  in  all  cases  very  thin,  the  amount 
of  gold  deposited  corresponding  to  the  quantity  of  basis-metal 
which  has  been  dissolved. 

III.  One  of  the  best  directions  for  gilding  without  the  use  of 
a  current  is,  according  to  the  "  Edelmetallindustrie,"  as  follows : 
Prepare  a  solution  of  gold  in  aqua  regia  (2  parts  hydrochloric 
acid  and    I    part  nitric   acid).      The  solution  of  the  gold   is 
effected  in  a  porcelain    dish,  best    in  a  sand    or    water  bath, 
whereby  heavy  brown   acid   vapors    of    hyponitrous   acid  are 
evolved.     When  all   is  dissolved  allow  the  acid   to  evaporate 
until  the  fluid  has  acquired  a  deep   brown  color  and  no  more 
acid  vapors  arise.     Then,  after  cooling,  dilute  the  solution  with 
water  and  keep  it  in  a  bottle  for  future  use.     Next  dissolve  in 
the  bath  6^  drachms  of  potassa  aad  nj^  drachms  of  sodium 


310  ELECTRO-DEPOSITION    OF   METALS. 

phosphate,  and  add  enough  gold  solution  that  the  bath  con- 
tains about  2j£  drachms  of  gold.  To  this  bath,  containing 
about  8  to  10  quarts  of  fluid,  add  careiully,  with  constant 
stirring,  I  ^  ozs.  of  potassium  cyanide,  and  then  let  it  thor- 
oughly boil  for  some  time.  After  cooling  the  bath  to  about 
176°  or  158°  F.,  suspend  the  articles  in  it  and  keep  the  bath  at 
this  temperature.  The  bath  only  requires  an  occasional  addi- 
tion of  gold  solution  (when  the  gilding  becomes  gray  or  dirty), 
or  of  potassium  cyanide  (when  the  gilding  becomes  foxy),  and, 
with  proper  treatment,  can  be  used  for  a  long  time. 

Gilding  of  porcelain,  glass,  etc. — The  pyrophosphate  baths 
given  above  may  be  advantageously  employed  for  gilding 
porcelain,  glass,  stoneware,  etc.,  the  process  being  as  follows  : — 

Neutral  platinic  chloride  is  intimately  triturated  with  enough 
lavender  oil  to  form  a  thin  syrup.  Of  this  preparation  a 
scarcely  perceptible  film  is  applied  by  means  of  a  small  brush 
to  the  article  to  be  ornamented.  When  dry,  the  article  is  heated 
in  a  muffle  to  a  dark  red  heat.  At  this  temperature  the  essen- 
tial oil  partially  volatilizes,  while  another  portion  is  decom- 
posed, and  reduces  by  its  hydrogen  the  platinic  chloride  to 
metallic  platinum,  the  result  being  a  coating  of  metal  of  a  finely 
polished  appearance.  When  cold  the  article  is  immediately 
drawn  through  nitric  acid,  which  does  not  attack  the  platinum, 
but  removes  any  impurities  which  might  make  its  surface  dull. 
The  article  is  then  washed  in  a  large  quantity  of  water,  wrapped 
with  fine  brass  wire  in  such  a  manner  that  the  wire  touches  the 
platinized  places  at  many  points,  and  is  then  brought  into  the 
gold  bath.  In  a  few  minutes  the  platinum  is  coated  with  a 
beautiful  smooth  film  of  gold,  which  adheres  well,  and  only  re- 
quires rubbing  with  chamois. 

By  this  method  the  expensive  work  of  polishing  is  rendered 
unnecessary,  which  with  articles  having  many  depressed  places 
is  besides  almost  impossible.  If  the  gilding  is  too  red,  add  to 
the  bath  a  few  drops  of  the  double  cyanide  of  potassium  and 
silver. 

Gilding  by  friction. — This  process  is  variously  termed  gilding 


DEPOSITION    OF    GOLD.  311 

with  the  rag,  with  the  thumb,  with  the  cork.  It  is  chiefly  em- 
ployed upon  silver,  though  sometimes  also  upon  brass  and  cop- 
per. The  operation  is  as  follows:  Dissolve  1.12  to  1.69 
drachms  of  chloride  of  gold  in  as  little  water  as  possible,  to 
which  has  previously  been  added  0.56  drachm  of  saltpetre. 
Dip  in  this  solution  small  linen  rags,  and,  after  allowing  them 
to  drain  off,  dry  them  in  a  dark  place.  These  rags  saturated 
with  gold  solution  are  then  charred  to  tinder  at  not  too  great  a 
heat,  whereby  the  chloride  of  gold  is  reduced,  partially  to 
protochloride  and  partially  to  finely  divided  metallic  gold. 
This  tinder  is  then  rubbed  in  a  porcelain  mortar  to  a  fine  uni- 
form powder. 

To  gild  with  this  powder,  dip  into  it  a  charred  cork  moistened 
with  vinegar  or  salt  water  and  rub,  with  not  too  gentle  a  pres- 
sure, the  surface  of  the  article  to  be  gilded,  which  must  be 
previously  cleansed  from  adhering  grease.  The  thumb  of  the 
hand  may  be  used  in  place  of  the  cork,  but  in  both  cases  care 
must  he  had  not  to  moisten  it  too  much,  as  otherwise  the 
powder  takes  badly.  After  gilding  the  surface  may  be  care- 
fully burnished. 

For  gilding  by  friction  a  solution  of  chloride  of  gold  in  an 
excess  of  potassium  cyanide  may  also  be  used,  after  thickening 
the  solution  to  a  paste  by  rubbing  in  whiting.  The  paste  is 
applied  to  the  previously  zincked  metals  by  means  of  a  cork,  a 
piece  of  leather,  or  a  brush.  Martin  and  Peyraud,  the  origina- 
tors of  this  method,  describe  the  operation  as  follows :  Articles 
of  other  metals  than  zinc  are  placed  in  a  bath  consisting  of 
concentrated  solution  of  sal  ammoniac,  in  which  has  been 
placed  a  quantity  of  granulated  zinc.  The  articles  are  allowed 
to  boil  a  few  minutes,  whereby  they  acquire  a  coating  of  zinc. 
For  the  preparation  of  the  gilding  composition,  dissolve  11.28 
drachms  of  chloride  of  gold  in  a  like  quantity  of  water,  and  add 
a  solution  of  2.11  ozs.  of  potassium  cyanide  in  as  little  water  as 
possible  (about  2.8  ozs.).  Of  this  solution  add  so  much  to  a 
mixture  of  3.52  ozs.  of  fine  whiting  and  2.82  drachms  of  pul- 
verized tartar  that  a  paste  is  formed  which  can  *be  readily  ap- 


312  ELECTRO-DEPOSITION    OF   METALS. 

plied  with  a  brush  to  the  article  to  be  gilded.  When  the  arti- 
cle is  coated,  heat  it  to  between  140°  and  158°  F.  After 
removing  the  dry  paste  by  washing,  the  gilding  appears  and 
can  be  polished  with  the  burnisher. 

Fire  or  mercury  gilding. — Before  the  introduction  of  electro- 
plating, nearly  all  substantial  gilding  was  effected  by  this  pro- 
cess. However,  the  cost  is  much  greater,  the  execution  of  the 
process  presenting  many  difficulties,  and  besides  the  workman 
is  constantly  exposed  to  the  very  injurious  mercurial  vapors. 
The  resulting  gilding,  however,  is  distinguished  by  great  solidity. 

The  execution  of  fire  gilding  begins  with  the  preparation  of 
the  amalgam  of  gold.  For  this  purpose  put  a  weighed  quantity 
of  fine  gold  in  a  crucible  and  heat  to  dull  redness.  The  re- 
quisite proportion  of  mercury,  8  parts  to  I  of  gold,  is  now 
added,  and  the  mixture  is  stirred  with  a  slightly  crooked  iron 
rod,  the  heat  being  kept  up  until  the  gold  is  entirely  dissolved 
by  the  mercury.  Pour  the  amalgam  into  a  small  dish  about 
3  parts  filled  with  water,  and  work  about  with  the  fingers  under 
the  water  to  squeeze  out  as  much  of  the  excess  of  mercury  as 
possible.  To  facilitate  this  the  dish  is  slightly  inclined,  to  allow 
the  superfluous  mercury  to  flow  from  the  mass,  which  soon  ac- 
quires a  pasty  condition  capable  of  receiving  the  impression  of 
the  fingers.  Afterward  squeeze  the  amalgam  in  a  chamois 
leather  bag,  by  which  a  further  quantity  of  mercury  is  liberated. 
The  amalgam,  which  remains  after  this  final  treatment,  consists 
of  about  33  parts  of  mercury  and  57  parts  of  gold  in  100  parts. 
The  mercury  which  is  pressed  through  the  bag  retains  a  good 
deal  of  gold,  and  is  employed  in  preparing  fresh  batches  of 
amalgam.  It  is  important  that  the  mercury  employed  should 
be  pure. 

To  apply  the  amalgam,  a  solution  of  nitrate  of  mercury  is  em- 
ployed which  is  prepared  by  dissolving  in  a  glass  flask  100  parts 
of  mercury  in  no  parts  of  nitric  acid  of  specific  gravity  1.33, 
gentle  heat  being  employed  to  assist  the  chemical  action. 
The  red  fumes  given  off  must  be  allowed  to  escape  into  the 
chimney,  since  they  are  very  deleterious  when  inhaled.  When 


DEPOSITION   OF    GOLD.  313 

the  mercury  is  all  dissolved  the  solution  is  to  be  diluted  with 
about  25  times  its  weight  of  distilled  water,  and  bottled  for  use. 
The  pasty  amalgam  is  spread  with  the  blade  of  a  knife  upon 
a  hard,  flat  stone.  The  article,  after  being  well  cleaned  and 
scratch- brushed,  is  treated  as  follows:  Take  a  small  scratch- 
brush,  formed  of  stout  brass  wire,  dip  in  the  solution  of  nitrate 
of  mercury,  then  draw  over  the  amalgam ;  pass  the  brush  care- 
fully over  the  surface  to  be  gilded,  repeatedly  dipping  the 
brush  in  the  mercurial  solution  and  drawing  it  over  the  amal- 
gam until  the  entire  surface  is  uniformly  and  sufficiently 
coated.  Then  rinse  the  article  well,  and  dry.  The  next 
operation  is  the  evaporation  of  the  mercury.  For  this  pur- 
pose a  charcoal  fire,  resting  upon  a  cast-iron  plate,  has  been 
generally  adopted,  a  simple  hood  of  sheet-iron  being  the  only 
means  of  protection  from  the  injurious  effects  of  the  mercurial 
vapors.  When  the  amalgamated  article  is  rinsed  and  dried,  it 
is  exposed  to  the  glowing  charcoal,  turned  about  and  heated 
by  degrees  to  the  proper  point,  then  it  is  withdrawn  from  the 
fire  by  means  of  long  pincers  or  tongs.  The  article  is  then 
taken  in  the  left  hand,  which  should  be  protected  with  a  leather 
glove,  turned  over  the  fire  in  every  direction,  and  while  the 
mercury  is  volatilizing  the  article  should  be  struck  with  a  long- 
haired brush  to  equalize  the  amalgam  coating  and  force  it  upon 
such  parts  as  may  appear  to  require  it.  When  the  mercury 
has  become  entirely  volatilized  the  gilding  has  a  dull,  greenish- 
yellow  color.  If  any  bare  places  are  apparent,  they  are 
touched  up  with  amalgam  and  the  article  is  again  submitted  to 
the  fire,  care  being  taken  to  expel  the  mercury  gradually.  The 
article  is  then  well  scratch-brushed.  When  it  is  of  a  pale 
greenish  color,  heat  it  again  to  expel  any  remaining  mercury, 
when  it  acquires  the  orange-yellow  of  fine  gold.  If  required 
to  be  bright,  it  is  burnished  in  the  ordinary  way.  If  the  gild- 
ing is  to  be  dead,  secure  the  article  by  means  of  iron  wire  to 
the  end  of  an  iron  rod  and  coat  it  with  a  hot  paste  consist- 
ing of  saltpetre,  common  salt,  and  alum ;  then  expose  the 
article  to  a  bright  fire,  turning  it  in  every  direction  until  the 


3  14  ELECTRO  DEPOSITION    OF   METALS. 

coat  of  the  mixture  fuses  and  begins  to  run  off;  then  remove 
the  article  from  the  fire  and  throw  it  in  a  wooden  vat  contain- 
ing a  large  quantity  of  water.  The  coat  of  salts  covering  the 
article  is  immediately  dissolved,  and  the  gilding  presents  a 
beautiful  dead  appearance.  To  stand  this  process  of  deadening 
the  article  must  be  well  gilded,  especially,  as  frequently  hap- 
pens, if  the  operation  does  not  succeed  the  first  time. 

Red  streaks  are  often  observed  on  otherwise  successful  gild- 
ing. These  streaks  are  caused  by  the  iron  wire  which  has 
been  wrapped  round  the  article.  They  disappear  by  plunging 
the  article  in  dilute  nitric  acid,  or,  still  better,  in  pure  hydro- 
chloric acid. 

For  the  sake  of  completeness,  a  method  of  gilding  which 
gives  to  some  parts  of  the  article  a  lustrous  and  to  others  a 
dead  appearance  may  here  be  mentioned.  It  is  a  combination 
of  fire-gilding  with  electro-deposition,  the  dead  places  being  pro- 
duced by  the  former  operation  and  the  lustrous  places  by  the 
latter.  The  operation  is  as  follows :  The  places  which  are  to 
be  dead  are  first  gilded  with  amalgam,  heated,  scratch-brushed 
and  raised.  The  entire  article  is  then  gilded  with  the  assistance 
of  the  battery,  no  attention  being  paid  to  any  gold  depositing 
upon  the  surfaces  already  gilded.  The  entire  surface  is  then 
carefully  scratch-brushed,  and  the  elecltro-gilded  surfaces  are 
next  coated  with  a  paste  of  flake-white,  water  and  glue,  and  then 
with  a  thick  paste  of  clay,  the  fire-gilded  surfaces  remaining 
free.  The  whole  is  then  allowed  to  dry,  when  the  fire-gilded 
surfaces  are  deadened  by  being  treated,  as  above  described,  with 
a  hot  paste  of  saltpetre,  common  salt,  and  alum.  The  coatings 
of  flake-white  and  clay  are  then  dissolved  by  means  of  water 
acidulated  with  hydrochloric  acid.  The  only  purpose  of  these 
coatings  is  to  prevent  a  too  intense  action  of  the  heat  upon  the 
electro-gilded  portions.  The  latter,  if  necessary,  are  then  again 
scratch-brushed,  which  must,  however,  be  done  with  the  greatest 
care  to  avoid  injury  to  the  dead  portions.  The  article  is  finally 
polished. 

The  following  process,  however,  is  better  and  more  con- 
venient:— 


DEPOSITION   OF    GOLD.  315 

The  surfaces  which  are  to  remain  dead  are  first  gilded  and 
deadened,  and  then  coated  with  varnish.  When  dry  the  article 
is  pickled ;  the  acid  does  not  attack  the  varnished  surfaces. 
The  object  is  then  brought  into  the  electro-gilding  bath,  which 
also  does  not  attack  the  varnish.  When  the  desired  shade  of 
gold  has  been  obtained,  the  article  is  taken  from  the  bath  and 
the  varnish  removed  by  means  of  benzine.  The  article  is  then 
washed  in  a  warm  potassium  cyanide  solution,  next  in  boiling 
water,  and  finally  dried.  The  dead  gilding,  no  matter  by  which 
process  it  may  have  been  produced,  is  only  suitable  for  arti- 
cles not  exposed  to  friction,  a  slight  touch  with  the  fingers 
being  sufficient  to  deprive  it  of  its  delicate  lustre. 

Old  dead  gilding  may  be  improved  by  boiling  with  potash 
and  washing  in  dilute  sulphuric  or  nitric  acid.  This  suffices 
for  the  removal  of  stains  caused  by  grease,  smoke,  or  dust.  If, 
however,  the  gilding  is  worn  off,  the  article  has  to  be  scratch- 
brushed  and  regilt. 

Du  Fresne  gives  a  method  of  gilding,  which  is  also  a  com- 
bination of  fire-gilding  with  electro-deposition.  It  is  executed 
as  follows : — 

The  articles  are  galvanized  with  the  assistance  of  the  current, 
in  a  mercurial  solution  consisting  of  cyanide  of  mercury  in 
potassium  cyanide,  with  additions  of  carbonate  and  phosphate 
of  soda,  then  gilded  in  an  ordinary  gilding  bath,  next  again 
coated  with  mercury,  then  again  gilded,  and  so  on,  until  a  de- 
posit of  sufficient  thickness  is  obtained.  The  mercury  is  then 
evaporated  over  glowing  coals,  and  the  articles,  after  scratch- 
brushing,  are  burnished. 

According  to  another  process,  the  articles  are  gilded  in  a  bath 
consisting  of  98  per  cent,  potassium  cyanide  1.2  ozs.,  cyanide 
of  gold  92^  grains,  cyanide  of  mercury  92^  grains,  distilled 
water  I  quart,  a  strong  current  being  used.  The  articles  being 
sufficiently  gilded,  the  mercury  is  evaporated,  the  articles 
scratch-brushed  and  finally  polished. 

Removing  gold  from  gilded  articles — "  Stripping." — Gilded 
articles  of  iron  and  steel  are  best  stripped  by  treating  them  as 


3l6  ELECTRO-DEPOSITION    OF   METALS. 

the  anode  in  a  solution  of  from  2  to  2^  ozs.  of  98  per  cent, 
potassium  cyanide  in  I  quart  of  water,  and  suspending  a  copper 
plate  greased  with  oil  or  tallow  as  the  cathode.  Gilded  silver- 
ware is  readily  stripped  by  heating  to  glowing  and  then  im- 
mersing in  dilute  sulphuric  acid,  whereby  the  layer  of  gold  cracks 
off,  the  glowing  and  subsequent  immersion  in  dilute  sulphuric 
acid  being  repeated  until  all  the  gold  is  removed.  Before  glow- 
ing and  immersing  in  dilute  sulphuric  acid,  the  articles  may  first 
be  provided  with  a  coating  of  a  paste  of  sal  ammoniac,  flowers  of 
sulphur,  borax,  and  nitrate  of  potash,  which  is  allowed  to  dry. 
On  the  bottom  of  the  vessel  containing  the  dilute  sulphuric  acid 
the  gold  will  be  found  in  laminae  and  scales,  which  are  boiled 
with  pure  sulphuric  acid,  washed,  and  finally  dissolved  in  aqua 
regia,  and  made  into  chloride  of  gold  or  fulminating  gold. 

To  strip  articles  of  silver,  copper,  or  German  silver  which  will- 
not  bear  glowing,  the  solution  of  gold  may  be  effected  in  a  mix- 
ture of  I  Ib.  of  fuming  sulphuric  acid,  2.64  ozs.  of  concentrated 
hydrochloric  acid,  and  1.3  ozs.  of  nitric  acid  of  40°  Be.  Dip 
the  articles  in  the  warm  acid  mixture  and  observe  the  pro- 
gressive action  of  the  mixture  by  frequently  removing  the 
articles  from  it.  The  articles  to  be  treated  must  be  perfectly 
dry  before  immersing  in  the  acid  mixture,  and  care  must  be 
had  to  preserve  the  latter  from  dilution  with  water  in  order  to 
prevent  the  acids  from  acting  upon  the  basis-metal. 

Determination  of  genuine  gilding. — Objects  apparently  gilded 
are  rubbed  upon  the  touchstone,  and  the  streak  obtained  is 
treated  with  pure  nitric  acid  •  of  1.30  to  1.35  specific  gravity. 
The  metal  contained  in  the  streak  thereby  dissolves,  and  as  far 
as  it  is  not  gold  disappears,  while  the  gold  remains  behind. 
The  stone  should  be  thoroughly  cleansed  before  each  operation, 
and  the  streak  should  be  made  not  with  an  edge  or  a  corner  of 
the  object  to  be  tested,  but  with  a  broader  surface.  If  no  gold 
remains  upon  the  stone,  but  there  is,  nevertheless,  a  suspicion 
of  the  article  being  slightly  gilded,  proceed  with  small  articles 
as  follows  :  Take  hold  of  the  article  with  a  pair  of  tweezers,  and 
after  washing  it  first  with  alcohol,  and  then  with  ether, .  and 


DEPOSITION    OF    GOLD.  317 

drying  upon  blotting  paper,  pour  over  it  in  a  test  glass,  cleansed 
with  alcohol  or  ether,  according  to  the  weight  of  the  article, 
0.084  to  5.64  drachms  of  nitric  acid  of  1.30  specific  gravity  free 
from  chlorine.  The  article  will  be  immediately  dissolved,  and 
if  it  has  been  gilded  never  so  slightly,  perceptible  gold  spangles 
will  remain  upon  the  bottom  of  the  glass. 

Recovery  of  gold  from  gold  baths,  etc. — To  recover  the  gold 
from  old  cyanide  gilding  baths,  evaporate  the  bath  to  dryness, 
mix  the  residue  with  litharge,  and  fuse  the  mixture.  The  gold 
is  contained  in  the  lead  button  thus  obtained.  The  latter  is 
then  dissolved  in  nitric  acid,  whereby  the  gold  remains  behind 
in  the  form  of  spangles.  These  spangles  are  filtered  off  and 
dissolved  in  aqua  regia. 

The  following  method  is  used  for  the  recovery  of  gold  by  the 
wet  process:  The  bath  containing  gold,  silver,  and  copper  is 
acidulated  with  hydrochloric  acid,  which  causes  a  disengage- 
ment of  hydrocyanic  acid.  This  gas  is  extremely  poisonous, 
for  which  reason  the  operation  should  be  carried  on  in  the  open 
air  or  where  there  is  a  good  draught  or  ventilation  to  carry  off 
the  fumes.  A  precipitate  consisting  of  the  cyanides  of  gold 
and  copper  and  chloride  of  silver  is  formed.  This  is  well 
washed  and  boiled  in  aqua  regia,  which  dissolves  the  gold  and 
copper  as  chlorides,  leaving  the  chloride  of  silver  behind.  The 
solution  containing  the  gold  and  copper  is  evaporated  nearly 
to  dryness  in  order  to  remove  the  excess  of  acid,  the  residue  is 
dissolved  in  a  small  quantity  of  water,  and  the  gold  precipitated 
therefrom  as  a  brown  metalic  powder  by  the  addition  of 
sulphate  of  iron  (copperas).  The  copper  remains  in  solution. 

Finely  divided  zinc — so-called  zinc-dust — is  an  excellent 
agent  for  the  precipitation  of  gold  in  a  pulverulent  form  from 
cyanide  gilding  baths.  By  adding  zinc  dust  to  an  exhausted 
cyanide  gilding  bath,  and  throroughly  shaking  or  stirring  it 
from  time  to  time,  all  the  gold  is  precipitated  in  two  or  three 
days.  The  quantity  of  zinc  required  for  precipitation  depends 
of  course  on  the  quantity  of  gold  present,  but  generally  speak- 
ing* /^  lb.  or  at  the  utmost  I  Ib.  of  zinc-dust  will  be  required 
for  [OO  quarts  of  exhausted  gilding  bath. 


ELECTRO-DEPOSITION    OF   METALS. 

The  pulverulent  gold  obtained  is  washed,  treated  first  with 
hydrochloric  acid  to  remove  adhering  zinc -dust,  and  next  with 
nitric  acid  to  free  it  from  silver  and  copper. 

From  the  acid  mixtures  serving  for  dead  pickling  gold,  or 
for  stripping,  the  gold  is  precipitated  by  solution  of  sulphate  of 
iron  (copperas)  added  in  excess.  The  gold  present  is  precipi- 
tated as  a  brown  powder  mixed  with  ferric  oxide.  This 
powder  is  filtered  off  and  treated  in  a  porcelain  dish  with  hot 
hydrochloric  acid,  which  dissolves  the  iron.  The  gold  which 
remains  behind  is  then  filtered  off,  and,  after  washing,  dissolved 
in  aqua  regia  in  order  to  work  the  solution  into  fulminating 
gold  or  neutral  chloride  of  gold. 


CHAPTER  XL 

DEPOSITION    OF   PLATINUM   AND    PALLADIUM, 
i   DEPOSITION  OF  PLATINUM. 

Properties  of  platinum. — Pure  platinum  is  white  with  a  grayish 
tinge  ;  it  is  as  soft  as  copper,  malleable,  and  very  ductile.  At  a 
white  heat  it  can  be  welded,  but  is  fusible  only  with  the  oxyhy- 
drogen  blowpipe  or  by  the  electric  current.  Its  specific  gravity 
is  21.4. 

Air  has  no  oxidizing  action  upon  platinum ;  it  is  scarcely 
acted  upon  by  any  single  acid ;  prolonged  boiling  with  con- 
centrated sulphuric  acid  appears  to  dissolve  the  metal  slowly. 
The  best  solvent  for  it  is  aqua  regia,  which  forms  the  tetrachlo- 
ride,  PtCl4.  Chlorine,  bromine,  sulphur,  and  phosphorus  com- 
bine directly  with  platinum,  and  fusing  saltpetre  and  caustic 
alkali  attack  it. 

Besides,  in  the  malleable  and  fused  state,  platinum  may  be 
obtained  as  a  very  finely  divided  powder,  the  so  -called  platinum 


DEPOSITION    OF    PLATINUM    AND    PALLADIUM.  319 

black,  which  is  precipitated  with  zinc  from  dilute  solution  of 
platinum  chloride  acidulated  with  hydrochloric  acid. 

Platinum  baths. — In  view  of  the  valuable  properties  of 
platinum  of  oxidizing  only  under  certain  difficult  conditions, 
of  possessing  an  agreeable  white  color,  and  of  taking  a  fine 
polish,  it  seems  strange  that  greater  attention  has  not  been 
paid  to  the  electro-deposition  of  this  metal  than  is  actually 
the  case.  The  reason  for  this  may  perhaps  be  found  in  the 
fact  that  the  baths  formerly  employed  for  experiments  pos- 
sessed many  great  defects,  causing  the  operator  many  diffi- 
culties, and  besides  allowed  only  of  the  production  of  thin 
deposits.  Giving  due  consideration  to  the  requirements  of  the 
process  of  the  electro-deposition  of  platinum  and  with  the  use 
of  a  suitable  bath,  deposits  of  platinum  of  a  certain  thickness 
can  be  readily  produced,  and  necessary  conditions  will  be  de- 
scribed under  "Treatment  of  platinum  baths." 

The  platinum  baths  formerly  proposed  did  not  yield  quite 
satisfactory  results,  the  content  of  platinum  being  too  small  in 
some  of  them,  while  with  others  dense  deposits  could  not  be 
obtained.  A  more  recent  formula  by  Boettger,  however,  gives 
a  quite  good  bath.  A  moderately  dilute  solution  of  sodium 
citrate  is  added  to  platoso-ammonium  chloride  until  an  excess 
of  the  latter  no  longer  dissolves,  even  after  continued  boiling. 
The  following  proportions  have  been  found  very  suitable.  Dis- 
solve 17^  ozs.  of  citric  acid  in  2  quarts  of  water,  and  neutral- 
ize with  caustic  soda.  To  the  boiling  solution  add,  with  con- 
stant stirring,  the  platoso-ammonium  chloride  freshly  precipi- 
tated from  2.64  ozs.  of  chloride  of  platinum,  heat  until  solution 
is  complete,  allow  to  cool,  and  dilute  with  water  to  5  quarts. 
To  decrease  the  resistance  of  the  bath,  0.7  or  O.8  oz.  of  sal 
ammoniac  may  be  added;  a  larger  addition,  however,  will 
cause  the  separation  of  dark-colored  platinum. 

The  platoso-ammonium  chloride  is  prepared  by  adding  to  a 
concentrated  solution  of  chloride  of  platinum  concentrated 
solution  of  sal  ammoniac  until  a  yellow  precipitate  is  no  longer 
formed  on  adding  a  further  drop  of  sal  ammoniac.  The  preci- 


320  ELECTRO-DEPOSITION    OF   METALS. 

pitate  is  filtered  off  and  brought  into  the  boiling  solution  of 
sodium  citrate.  This  bath  works  very  uniformly  if  the  content 
of  platinum  is  from  time  to  time  replenished. 

"  The  Bright  Platinum  Plating  Company,"  of  London,  has 
patented  the  following  composition  of  a  platinum  bath: 
Chloride  of  platinum  0.98  oz.,  sodium  phosphate  19^  ozs., 
ammonium  phosphate  3.95  ozs.,  sodium  chloride  0.98  oz.,  and 
borax  0.35  oz.,  are  dissolved,  with  the  aid  of  heat,  in  6  to  8 
quarts  of  water,  and  the  solution  is  boiled  for  10  hours,  the 
water  lost  by  evaporation  being  constantly  replaced.  The  re- 
sults obtained  with  this  bath  were  not  much  better  than  with 
Bottger's. 

Dr.  W.  H.  Wahi  gives  the  following  directions  for  preparing 
platinum  baths:* — 

Alkaline  platinate  bath. — Platinic  hydrate  2  ozs.,  caustic 
potassa  (or  soda)  8  ozs.,  distilled  water  I  gallon. 

Dissolve  one-half  of  the  caustic  potassa  in  a  quart  of  distilled 
water,  add  to  this  the  platinic  hydrate  in  small  quanrity  at  a 
time,  facilitating  solution  by  stirring  with  a  glass  rod.  When 
solution,  is  effected,  stir  in  the  other  half  of  alkali  dissolved  in  a 
quart  of  water ;  then  dilute  with  enough  dfstilled  water  to  form 
one  gallon  of  solution.  To  hasten  solution,  the  caustic  alkali 
may  be  gently  heated,  but  this  is  not  necessary,  as  the  platinic 
hydrate  dissolves  very  freely.  This  solution  should  be  worked 
with  a  current  of  about  two  volts,  and  will  yield  metal  of  an  al- 
most silvery  whiteness  upon  polished  surfaces  of  copper  and 
brass,  and  quite  freely.  There  should  be  slight,  if  any,  percep- 
tible evolution  of  hydrogen  at  the  cathode,  but  a  liberal  evolu- 
tion of  oxygen  at  the  anode.  An  addition  of  a  small  proportion 
of  acetic  acid  to  this  bath  improves  its  operation  where  a  heavy 
deposit  is  desired.  The  anode  must  be  of  platinum  or  carbon, 
and  owing  to  the  readiness  with  which  the  metal  is  deposited 
an  excess  of  anode-surface  is  to  be  avoided.  Articles  of  steel, 
nickel,  tin,  zinc,  or  German  silver  will  be  coated  with  black  and 

*  Journal  of  the  Franklin  Institute,  July,  1890. 


DEPOSITION   OF    PLATINUM   AND    PALLADIUM.  321 

more  or  less  non-adherent  platinum  ;  but  by  giving  objects  of 
these  metals  a  preliminary  thin  electro-deposit  of  copper  in  the 
hot  cyanide  bath  they  may  be  electro-platinized  in  the  alkaline 
platinate  bath  equally  as  well  as  copper.  The  bath  may  be 
worked  hot  or  cold,  but  it  is  recommended  to  work  it  at  a  tem- 
perature not  exceeding  100°  F.  It  may  be  diluted  to  one-half 
the  strength  indicated  in  the  formula  and  still  yield  excellent 
results.  The  surface  of  the  objects  should  be  highly  polished 
by  buffing  or  otherwise  prior  to  their  introduction  into  the  bath, 
if  the  resulting  deposit  is  designed  to  be  brilliant. 

The  deposition  of  platinum  takes  place  promptly.  In  five 
minutes  a  sufficiently  heavy  coating  will  be  obtained  for  most 
purposes.  The  deposited  metal  is  so  soft,  however,  that  it  re- 
quires to  be  buffed  very  lightly.  A  heavier  deposit  will  appear 
gray  in  color,  but  will  accept  the  characteristic  lustre  of  platinum 
beneath  the  burnisher. 

An  oxalate  solution  is  prepared  by  dissolving  i  oz.  of  platinic 
hydrate  in  4  ozs.  of  oxalic  acid  and  diluting  the  solution  to  the 
volume  of  one  gallon  with  distilled  water.  The  solution  should 
be  kept  acidified  by  the  occasional  addition  of  some  oxalic  acid. 
The  simplest  plan  of  using  this  bath,  which  requires  no  atten- 
tion to  proportions,  is  simply  to  work  with  a  saturated  solution 
of  the  oxalate,  keeping  an  undissolved  excess  always  present  at 
the  bottom  of  the  vessel.  An  addition  of  a  small  quantity  of 
oxalic  acid  now  and  then  will  be  found  advantageous.  The 
double  salts  of  oxalic  acid  with  platinum  and  the  alkalies  may 
be  formed  by  saturatfng  the  binoxalate  of  the  desired  alkali  with 
platinic  hydrate  and  maintaining  the  bath  in  normal  metallic 
strength  by  the  presence  of  an  undissolved  residuum  of  platin- 
ous  oxalate. 

The  double  oxalates  are  not  so  soluble  in  water  as  the  simple 
salt.  The  oxalate  baths,  both  of  single  and  double  salts,  may  be 
worked  cold  or  hot  (though  not  to  exceed  150°  F.)  with  a 
current  of  comparatively  low  pressure.  The  metal  will  deposit 
bright,  reguline,  and  adherent  on  copper  and  brass.  Other 
metallic  objects  must  receive  a  preliminary  coppering  as  above. 

21 


322  ELECTRO-DEPOSITION    OF   METALS. 

The  deposited  metal  is  dense,  with  a  steely  appearance,  and 
can  be  obtained  of  any  desired  thickness. 

The  deposit  obtained  in  the  oxalate  bath  is  sensibly  harder 
than  that  from  the  alkaline  platinate  bath,  and  will  bear  buffing 
tolerably  well. 

The  phosphate  bath  may  be  prepared  by  the  following 
formula : 

Phosphoric  acid,  syrupy  (specific  gravity  1.7),  8  ozs., 
platinic  hydrate  I  to  I  J^  ozs.,  distilled  water  I  gallon. 

The  acid  should  be  moderately  diluted  with  distilled  water 
and  the  solution  of  the  hydrate  effected  at  the  boiling  tempera- 
ture. Water  should  be  added  cautiously  from  time  to  time  to 
supply  that  lost  by  evaporation.  When  solution  has  taken 
place,  the  same  should  be  diluted  with  sufficient  water  to  make 
the  volume  I  gallon.  The  solution  may  be  worked  cold  or 
heated  to  100°  F.,  and  with  a  current  much  stronger  than  that 
required  for  the  platinates  and  oxalates.  The  ammonio  (and 
sodio)  platinic  phosphates  may  be  formed  from  the  simple 
phosphate  by  carefully  neutralizing  the  solution  of  the  phos- 
phate with  ammonia  (or  soda)  ;  then  adding  an  excess  of 
phosphoric  acid,  or  enough  to  dissolve  the  precipitate  formed, 
and  an  additional  quantity  to  insure  a  moderate  amount  of  free 
phosphoric  acid  in  the  bath.  The  phosphate  baths  will  be 
maintained  of  normal  strength  by  additions  of  platinic  hydrate, 
the  solutions  of  which  will  need  to  be  assisted  by  heating  the 
bath,  preferably  at  the  close  of  each  day's  work.  The  metal 
yielded  by  the  electrolysis  of  these  phosphate  solutions  is 
brilliant  and  adherent.  It  has  the  same  steely  appearance  as 
that  exhibited  by  the  oxalate  solutions,  but  to  a  less  pro- 
nounced degree.  The  physical  properties  of  the  deposited 
metal  are  in  other  respects  like  those  described  in  connection 
with  that  obtained  from  the  oxalate  baths. 

Management  of  platinum  baths. — Copper  and  brass  may  be 
directly  coated  with  platinum,  but  iron,  steel,  and  other  metals 
have  to  be  previously  coppered  ;  without  preliminary  copper- 
ing these  metals  would  soon  decompose  the  platinum  bath, 


DEPOSITION    OF   PLATINUM   AND   PALLADIUM.  323 

independent  of  the  fact  that  no  perfect  deposit  of  platinum  can 
be  produced  upon  them  without  the  cementing  intermediary 
layer  of  copper. 

Platinum  baths  must  be  used  hot,  and  even  then  require  a 
current  of  5  to  6  volts.  An  abundant  evolution  of  gas  must 
appear  on  the  objects  and  the  anodes ;  the  anode-surface 
(platinum  anodes)  must  not  be  too  small,  and  should  be  only  at 
a  few  centimetres  distance  from  the  objects.  Since  the  platinum 
anodes  do  not  dissolve,  the  content  of  platinum  in  the  bath  be- 
comes constantly  smaller,  and  the  bath  must  from  time  to  time 
be  strengthened.  It  is  then  heated  in  a  porcelain  dish  or  en- 
ameled vessel  to  the  boiling-point,  some  fresh  solution  of  sodium 
citrate  is  added,  and  platoso-ammonium  chloride  introduced  as 
long  as  solution  takes  place.  A  concentrated  solution  of 
platoso-ammonium  chloride  may  be  kept  at  hand  and  a  small 
quantity  of  it  at  intervals  be  added  to  the  bath. 

Execution  of  platinizing, — The  objects  thoroughly  freed  from 
grease  and  pickled,  and,  if  necessary,  coppered,  are  suspended 
in  the  bath  heated  to  between  176°  and  194°  F. ;  this  tempera- 
ture must  be  kept  up  during  the  entire  operation.  The  current 
should  be  of  sufficient  strength  and  the  anodes  placed  so  close 
to  the  objects  that  a  liberal  evolution  of  gas  appears  on  the 
anodes.  For  platinizing  large  objects  it  is  recommended  to  go 
round  them,  at  a  distance  of  0.31  to  0.39  inch,  with  a  hand- 
anode  of  platinum  sheet,  which  should  not  be  too  small  and 
should  be  connected  to  the  anode-rod.  When  the  current  has 
vigorously  acted  for  8  to  10  minutes,  the  objects  are  taken  from 
the  bath,  dried,  and  polished.  However,  for  the  production  of 
heavy  deposits — for  instance,  upon  points  of  lightning-rods — 
the  deposit  is  vigorously  brushed  with  a  steel-wire  scratch-brush 
or  fine  pumice  powder.  The  objects  are  then  once  more  freed 
from  grease  and  returned  for  10  to  15  minutes  longer  to  the 
bath  to  receive  a  further  deposit  of  platinum  with  a  weaker  cur- 
rent, which  must,  however,  be  strong  enough  to  cause  the 
escape  of  an  abundance  of  gas-bubbles.  The  objects  are  then 
taken  out,  and,  after  immersion  in  hot  water,  dried  in  sawdust. 


324  ELECTRO-DEPOSITION   OF   METALS. 

The  deposit  is  then  well  burnished,  first  with  the  steel  tool, 
and  finally  with  the  stone,  whereby  the  gray  tone  disappears 
and  the  deposit  shows  the  color  and  lustre  of  massive  platinum 
sheet.  Points  of  lightning-rods  platinized  in  this  manner  were 
without  flaw  after  an  exposure  to  atmospheric  influences  for 
more  than  six  years. 

Platinizing  of  glass. — Glass  may  be  platinized  by  means  of 
the  galvanic  current  as  follows  :  Dissolve  14  drachms  of  platinic 
hydrate  in  17^  ozs.  of  a  10  per  cent,  solution  of  caustic  soda 
or  potash.  Add  to  the  solution  17^  ozs.  more  of  the  alkali 
solution  and  dilute  with  water  to  2  quarts.  The  temperature  of 
the  bath  should  not  exceed  100°  F.,  and  the  strength  of  the 
current  should  be  two  volts. 

Platinizing  by  contact. — Though  a  thick  deposit  cannot  be 
produced  by  the  contact-process,  Fehling's  directions  may  here 
be  mentioned  as  suitable  for  giving  a  thin  coat  of  platinum  to 
fancy  articles.  He  recommends  a  solution  of  5.64  drachms  of 
chloride  of  platinum  and  7  ozs.  of  common  salt  in  I  quart  of 
water,  which  is  made  alkaline  by  the  addition  of  a  small  quantity 
of  soda  lye,  and  for  use  heated  to  the  boiling  point. 

If  larger  articles  are  to  be  platinized  by  contact,  free  them 
from  grease,  and  after  pickling,  and  if  necessary,  coppering, 
wrap  them  round  with  zinc  wire  or  place  them  upon  a  bright 
zinc  sheet  and  introduce  them  into  the  heated  bath.  All  the 
remaining  manipulations  are  the  same  as  in  other  contact  pro- 
cesses. 

Recovery  of  platinum  from  platinum  solutions. — From  not  too 
large  baths,  precipitation  of  the  platinum  with  sulphuretted 
hydrogen  is  the  most  suitable  method,  and  preferable  to  evapo- 
rating and  reducing  the  metal  from  the  residue.  The  process  is 
as  follows:  Acidulate  the  platinum  solution  with  hydrochloric 
acid,  and,  after  warming  it,  conduct  sulphuretted  hydrogen  into 
it.  The  metal  (together  with  any  copper  present)  precipitates 
as  sulphide  of  platinum.  The  precipitate  is  filtered  off,  dried, 
.and  glowed  in  the  air,  whereby  metallic  platinum  remains  be- 
hind. From  larger  baths  the  platiuum  may  be  precipitated  by 


DEPOSITION    OF    PLATINUM    AND    PALLADIUM.  325 

suspending  bright  sheets  of  iron  in  the  acidulated  bath.  In 
both  cases  the  precipitated  platinum  is  treated  with  dilute  nitric 
acid  in  otder  to  dissolve  any  copper  present.  After  filtering  off 
and  washing  the  pure  platinum,  dissolve  it  in  aqua  regia;  the 
solution  is  then  evaporated  to  dryness  in  the  water  bath,  and 
the  chloride  of  platinum  thus  obtained  may  be  used  in  making 
a  new  bath. 

2.  Deposition  of  Palladium. 

Properties  of  palladium. — Palladium,  when  compact,  has  a 
white  color  and  possesses  a  lustre  almost  equal  to  that  of  silver. 
Its  specific  gravity  is  about  1 2.0;  it  is  malleable  and  ductile, 
and  may  be  fused  at  a  white  heat.  In  the  oxyhydrogen  flame 
it  is  volatilized,  forming  a  green  vapor.  It  is  less  permanent  in 
the  air  than  platinum.  It  is  dissolved  by  nitric  acid ;  it  is 
scarcely  attacked,  however,  by  hydrochloric  or  sulphuric  acid. 
Hydriodic  acid  and  free  iodine  coat  it  with  the  black  palladium 
iodide. 

On  account  of  the  high  price  of  its  salts,  palladium  has  been 
but  little  used  for  electro-plating  purposes ;  nor  for  the  same 
reason,  is  it  likely  to  be  more  extensively  employed  in  the 
future. 

According  to  M.  Bertrand,  the  most  suitable  bath  consists  of 
a  neutral  solution  of  the  double  chloride  of  palladium  and 
ammonium,  which  is  readily  decomposed  by  3  Bunsen  ele- 
ments coupled  one  behind  the  other  (therefore  about  5.4  volts). 
A  sheet  of  palladium  is  used  as  anode. 

A  solution  of  palladium  cyanide  in  potassium  cyanide  does 
not  yield  as  good  results  as  the  above  bath. 

Palladium  possessing  the  property  of  not  being  blackened  by 
sulphuretted  hydrogen,  it  is  for  this  reason  frequently  used  for 
coating  silver-plated  metallic  articles  with  a  thin  deposit  of  it. 

Palladium  has  also  of  recent  years  been  employed  for  plat- 
ing watch  movements.  According  to  M.  Pilet,  4  milligrammes 
(about  Ty  grain)  of  palladium  is  sufficient  to  coat  the  works  of 
an  ordinary  sized  watch.  M.  Pilet  recommends  the  following 


326  ELECTRO-DEPOSITION    OF   METALS. 

bath:  Water  2  quarts,  chloride  of  palladium  5^  drachms, 
phosphate  of  ammonia  3^  ozs.,  phosphate  of  soda  17^  ozs., 
benzoic  acid  2^  drachms. 

Deposits  of  iridium  and  rhodium  have  recently  been  produced 
from  baths  similar  in  composition  to  those  mentioned  under 
palladium.  But  as  these  metals  would  be  used  for  plating  pur- 
poses only  in  isolated  cases,  it  is  not  necessary  to  enter  into 
details. 


CHAPTER  XII. 

DEPOSITION  OF  TIN,  ZINC,  LEAD,  AND    IRON. 

i.  Deposition  of  Tin. 

Properties  of  tin. — Tin  is  a  white,  highly  lustrous  metal ;  it 
possesses  but  little  tenacity,  but  has  a  high  degree  of  malleabil- 
ity, and  tin-foil  may  be  obtained  in  leaves  less  than  sVth  of  a 
milli-metre  in  thickness.  Tin  melts  at  about  ^46°  F.  and  evap- 
orates at  a  high  temperature ;  the  fused  metal  shows  great 
tendency  to  crystallize  on  congealing.  By  treating  the  surface 
of  melted  tin  with  a  dilute  acid,  the  crystalline  structure  ap- 
pears as  designs  (moire  metallique),  resembling  the  ice-flowers 
on  frosted  windows. 

Tin  remains  quite  constant  even  in  moist  air,  and  resists  the 
influence  of  an  atmosphere  containing  sulphuretted  hydrogen. 
Strong  hydrochloric  acid  quickly  dissolves  tin  on  heating,  evolv- 
ing hydrogen  and  forming  stannous  chloride.  Dilute  sulphuric 
acid  has  but  little  action  on  the  metal ;  when  heated  with  con- 
centrated sulphuric  acid,  sulphur  dioxide  is  evolved.  Dilute 
nitric  acid  dissolves  tin  in  the  cold  without  evolution  of  gas ; 
concentrated  nitric  acid  acts  vigorously  upon  the  metal,  whereby 
oxide  of  tin,  which  is  insoluble  in  the  acid,  is  formed.  Alkaline 
lyes  dissolve  the  metal  to  sodium  stannate,  hydrogen  being 
thereby  evolved. 


DEPOSITION   OF   TIN,  ZINC,  LEAD,  AND    IRON.  327 

Tin  baths.  The  bath  used  by  Roseleur  for  tinning  with  the 
battery  works  very  well.  It  is  composed  as  follows : 

I.  Pyrophosphate  of  soda  3.5  ozs.,  tin-salt   (fused)  0.35  oz., 
water  10  quarts.     To  prepare  the  bath  dissolve  the  pyrophos- 
phate  of  soda  in  10  quarts  of  rain  water,  suspend  the  tin-salt  in 
a  small  linen  bag  in  the  solution,  and  move  the  bag  to  and  fro 
until  its  contents  are  entirely  dissolved. 

Objects  of  zinc,  copper,  and  brass  are  directly  tinned  in  this 
bath  with  a  current  of  slight  tension.  Articles  of  iron  and  steel  are 
first  coppered  or  preliminarily  tinned  in  a  bath  prepared  according 
to  formula  VIII.,  (see  p.  33  I )  the  deposit  of  tin  being  then  aug- 
mented in  bath  I.  with  the  battery  current.  Cast-tin  anodes  as 
large  as  possible  are  used,  which,  however,  will  not  keep  the  con- 
tent of  tin  in  the  bath  constant.  It  is  therefore  necessary,  from 
time  to  time,  to  add  tin-salt,  which  is  best  done  by  preparing  a 
solution  of  3.5  ozs.  of  pyrophosphate  of  soda  in  I  quart  of  water 
and  introducing  into  the  solution  tin  salt  as  long  as  the  latter 
dissolves  clear.  Of  this  tin  essence  add  to  the  bath  more  or 
less,  as  may  be  required,  and  also  augment  the  content  of  pyro- 
phosphate of  soda,  if,  notwithstanding  the  addition  of  tin-salt, 
the  deposition  of  tin  proceeds  sluggishly. 

Though  the  bath  composed  according  to  formula  I.  suffices 
for  most  purposes,  an  alkaline  tin  bath,  first  proposed  by  Eisner 
and  later  recommended  by  Maistrasse,  Fearn,  Birgham,  and 
others,  with  or  without  addition  of  potassium  cyanide,  may  be 
mentioned  as  follows:  — 

II.  Crystallized  tin-salt  0.7  oz.,  water  I  quart,  and  potash  lye 
of  10°  Beaume  until  the  precipitate  formed  dissolves. 

As  seen  from  the  formula  the  solution  of  tin-salt  is  com- 
pounded with  potash  lye  of  the  stated  concentration  (or  with  a 
solution  of  i  oz.  of  pure  caustic  potash  in  water),  until  the  pre- 
cipitate of  stannous  hydrate  again  dissolves. 

Some  operators  recommend  the  addition  of  0.35  oz.  of  potas- 
sium cyanide  to  the  solution. 

Without  potassium  cyanide  the  bath  requires  3.75  to  4  volts, 
and  with  it,  3.5  volts. 


328  ELECTRO-DEPOSITION   OF   METALS. 

In  testing  Salzede's  bronze  bath  (p.  247),  it  was  found  to 
yield  quite  a  good  deposit  of  tin  directly  upon  cast-iron,  and  it 
was  successfully  used  for  this  purpose  by  omitting  the  cuprous 
chloride  and  using  14.11  drachms  of  stannous  chloride,  so  that 
the  composition  became  as  follows :  — 

Ha.  98  per  cent,  potassium  cyanide  3.5  ozs.,  carbonate  of 
potassium  35j{  ozs.,  stannous  chloride  14.11  drachms,  water  10 
quarts.  With  4  volts  a  heavy  deposit  was  rapidly  obtained. 

III.  A  tin  bath  of  stannous  chloride,  caustic  soda,  and  potas- 
sium cyanide,  given  by  Pfanhauser,  contains   1 1  %  drachms  of 
stannous  chloride,  equal  to  about  7^  drachms  of  metallic  tin 
per  quart.     It  is   still   more  advantageous  to   use   double   the 
quantity   of  tin,  the   composition  of   the   bath  being    then   as 
follows :  — 

Water  10  quarts,  fused  stannous  chloride  14  ozs.,  caustic  soda 
17^?  ozs.,  100  per  cent,  potassium  cyanide  3^  ozs. 

The  bath,  as  above  composed,  contains  about  15  drachms  of 
metallic  tin  per  quart,  and  with  3^  volts  furnishes  a  deposit  of 
tin  of  about  4^  grains  per  hour. 

Pfanhauser  has  made  new  experiments  and  found  that  still 
more  favorable  results  are  obtained  with  a  solution  of  I  ^  ozs. 
of  stanno-ammonium  chloride  in  I  quart  of  water,  a  deposit  of 
9^>  grains  of  tin  per  hour  being  obtained  with  a  current  of 
only  \y2  volts. 

The  solution  of  the  salt  is  readily  effected.  Cast-tin  anodes 
are  to  be  used. 

The  temperature  of  the  bath  should  be  between  68°  and  77° 
F.  In  case  the  bath  becomes  poor  in  metal,  stanno-ammonium 
chloride  is  added. 

The  deposit  of  tin  is  rather  rough,  but  can  be  readily  made 
bright  by  treatment  with  brass  scratch-brushes. 

IV.  A  tin  bath  given  by  Taucher  is  composed  as  follows : 
Water  500  quarts,  sodium  or  pyrophosphate  1 1  Ibs.,  crystallized 
tin-salt  21  ozs.,  or,  still  better,  fused  tin-salt  17^  ozs. 

Bring  the  water  into  a  tank  completely  lined  with  plates  or 
anodes  of  tin  joined  together  and  connected  with  the  positive 


DEPOSITION    OF   TIN,  ZINC,  LEAD,  AND    IRON.  329 

pole  wire.  Dissolve  the  pyrophosphate  in  the  water,  stirring 
constantly.  Place  the  tin-salt  in  a  copper-sieve,  and  immerse 
the  latter  about  one-half  in  the  solution  ;  an  abundant  milky 
turbidity  is  immediately  formed,  which,  however,  disappears  on 
stirring.  When  all  the  tin-salt  is  dissolved,  remove  the  sieve, 
and  the  tin-bath,  which  now  forms  a  clear  fluid,  either  colorless 
or  of  a  slightly  yellowish  color,  is  ready  for  use,  it  being  only 
necessary  to  secure  the  articles  to  be  tinned  to  the  rods  con- 
nected with  the  negative  pole.  The  anodes  do  not  suffice  to 
keep  the  bath  saturated,  and  hence,  when  the  deposit  becomes 
weaker,  small  quantities  of  equal  parts  of  tin-salt  and  of  sodium 
pyrophosphate  have  to  be  added.  The  solution  of  these  salts 
should  always  be  effected  with  the  assistance  of  a  sieve  to  prevent 
small  pieces  of  tin-salt  from  falling  to  the  bottom  of  the  bath, 
where  they  would  be  enveloped  by  an  almost  insoluble  crust 
and  remain  nearly  unchanged. 

This  tin  bath  is  suitable  for  all  kinds  of  metals,  the  deposit 
obtained  combining  with  considerable  solidity  a  matted  and 
white  appearance  closely  resembling  silver. 

Management  of  tin  baths. — Tin  baths  should  not  be  used  at  a 
temperature  below  68°  F. ;  they  require  (formulae  I.  and  II.),. 
according  to  their  composition,  a  current  of  2  to  3  volts,  so  that 
two  Bunsen  elements  coupled  one  after  the  other  suffice  for  all 
purposes.  Too  strong  a  current  causes  a  pulverulent  reduction 
of  the  tin,  which  does  not  adhere  well,  while  with  a  suitable 
current-strength  quite  a  dense  and  reguline  deposit  is  obtained. 
Cast-tin  plates  with  as  large  a  surface  as  possible  are  used  as 
anodes.  The  choice  of  the  tin-salt  exerts  some  influence  upon 
the  color  of  the  tinning.  By  using,  for  instance,  crystallized  tin- 
salt,  which  is  always  acid,  in  preparing  the  bath  according  to 
formula  I.,  a  beautiful  white  tinning  with  a  bluish  tinge  is  ob- 
tained, which,  however,  does  not  adhere  so  well  as  that  pro- 
duced with  fused  tin- salt.  Again,  the  latter  yields  a  somewhat 
.dull  gray  layer  of  tin,  and,  therefore,  the  effects  of  the  bath 
will  have  to  be  corrected  by  the  addition  of  one  or  the  other 
salt. 


33°  ELECTRO-DEPOSITION    OF   METALS. 

As  previously  mentioned,  iron  and  steel  objects  are  best  sub- 
jected to  a  light  preliminary  tinning  by  boiling  in  the  bath  VIII. 
(see  p.  331 )  ;  however,  instead  of  this  preliminary  tinning,  they 
may  first  be  electro-coppered  and,  after  scratch-brushing  the 
copper  deposit,  brought  into  the  tin  bath. 

When  the  action  of  the  bath  becomes  sluggish,  it  has  to  be 
refreshed  (for  formula  I.)  by  the  addition  of  tin  salt  and  pyro- 
phosphate  of  soda,  or  (for  formula  II.)  by  the  addition  of  potash 
lye  and  tin-salt. 

Process  of  tinning. — From  what  has  been  said,  it  will  be  evi- 
dent that  the  execution  of  tinning  is  simple  enough.  After 
being  freed  from  grease  and  pickled,  the  objects  are  brought 
into  the  bath  and  tinned  with  a  weak  current.  For  heavy  de- 
posits of  tin  the  objects  are  frequently  taken  from  the  bath  and 
the  deposit  is  thoroughly  brushed  with  a  brass  scratch-brush, 
not  too  hard,  and  moistened  with  dilute  sulphuric  acid  (i  part 
acid  of  66°  Be.  to  25  water)  when,  after  rinsing  in  water,  the 
articles  are  returned  to  the  bath.  If,  with  the  use  of  too  strong 
a  current,  the  color  of  the  deposit  is  observed  to  turn  a  dark 
dull  gray,  scratch-brushing  must  be  repeated.  When  the  tin- 
ning is  finished  the  articles  are  brushed  with  a  brass  scratch- 
brush  and  decoction  of  soap-root,  then  dried  in  sawdust  and 
polished  with  fine  whiting. 

Tinning  by  contact  and  boiling. — For  tinning  by  zinc  contact 
in  the  boiling  tin  bath  the  following  solutions  may  be  recom- 
mended :  — 

V.  According  to   Gerhold :   Pulverized  tartar  and   alum,  of 
each  3.5   ozs.,  fused  stannous  chloride   14  drachms,  rain-water 
10  quarts. 

VI.  According  to  Roseleur:    Potassium  pyrophosphate /ozs., 
crystallized  stannous  chloride  (tin-salt),  n  drachms,  fused  Stan- 
nous  chloride  2.8  ozs.,  rain-water  10  quarts. 

VII.  According  to  Roseleur,  for  tinning  by  immersion  :  Potas- 
sium pyrophosphate  5.6  ozs.,  fused  stannous  chloride  1.23  ozs., 
rain-water  10  quarts. 

Formulae  V.  and  VI.  yield  good  results.     For  tinning  by  con- 


DEPOSITION    OF   TIN,  ZINC,  LEAD,  AND    IRON.  331 

tact,  heat  the  bath  to  boiling  and  suspend  the  clean  and  pickled 
objects  in  contact  with  pieces  of  zinc,  or,  better,  wrapped  around 
with  zinc  wire  spirals,  care  being  had  from  time  to  time  to  shift 
them  about  to  prevent  staining.  Large  baths  which  cannot  be 
readily  heated  are  worked  cold,  the  objects  being  covered  with 
a  large  zinc  plate  ;  in  the  cold  bath  the  formation  of  the  tin  de- 
posit requires,  of  course,  a  longer  time.  By  using  the  electric 
•current  the  deposit  can  be  made  as  heavy  as  desired.  By  im- 
mersion in  the  bath  prepared  according  to  formula  VII.,  zinc 
can  only  be  coated  with  a  very  thin  film  of  tin,  which,  however, 
by  the  use  of  a  battery,  can  be  made  as  heavy  as  desired. 

For  tinning  by  contact  in  a  cold  bath,  Zilken  has  patented 
the  following  solution:  Dissolve  with  the  aid  of  heat  in  100 
quarts  of  water,  tin-salt  7  to  10.5  ozs.,  pulverized  alum  10.5 
ozs.,  common  salt  15^  ozs.,  and  pulverized  tartar  7  ozs.  The 
cold  solution  forms  the  tin  bath.  The  objects  to  be  tinned  are 
to  be  wrapped  round  with  strips  of  zinc.  Duration  of  the  pro- 
cess 8  to  10  hours. 

Tinning  solution  for  iron  and  steel  articles. — VIII.  Crystal- 
lized ammonium-alum  7  ozs.,  crystallized  stannous  chloride  2.8 
drachms,  fused  stannous  chloride  2.8  drachms,  rain-water  10 
quarts  Dissolve  the  ammonium-alum  in  the  hot  water,  and 
when  dissolved  add  the  tin-salts.  The  bath  is  to  be  used  boil- 
ing hot  and  kept  at  its  original  strength  by  an  occasional  addi- 
tion of  tin-salt.  The  clean  and  pickled  iron  objects,  being 
immersed  in  the  bath,  become  in  a  few  seconds  coated  with  a 
firmly  adhering  film  of  tin  of  a  dead,  white  color,  which  may 
be  polished  by  scratch-brushing  or  scouring  with  sawdust  in 
the  tumbling  drum.  Tinning  by  boiling  in  this  bath  is  the 
most  suitable  preparation  for  iron  and  steel  objects,  which  are 
to  be  provided  with  a  heavy  electro-deposit  of  tin.  To  be  en- 
tirely sure  of  success  it  is  recommended  thoroughly  to  scratch- 
brush  the  objects,  then  to  return  them  once  more  to  the  bath, 
and  finally  to  suspend  them  in  a  bath  composed  according  to 
formula  I.  or  II. 

A  tinning  solution  for  small  brass  and  copper  articles  (pins, 


332  ELECTRO-DEPOSITION    OF   METALS. 

eyes,  hooks,  etc.),  consists  of  a  boiling  solution  of:  Pulverized 
tartar  3.5  ozs.,  stannous  chloride  (tin-salt)  14.11  drachms, 
water  10  quarts.  After  heating  the  bath  to  the  boiling-point, 
immerse  the  objects  to  be  tinned  in  a  tin  sieve  or  in  contact 
with  pieces  of  zinc ;  frequent  stirring  with  a  tin  rod  shortens 
the  process. 

Another  solution,  given  by  BSttger,  also  yields  good  results : 
Dissolve  oxide  of  tin  by  boiling  with  potash  lye,  and  place  the 
copper  or  brass  objects  to  be  tinned  in  the  boiling  solution  in 
contact  with  tin  shavings. 

Eisner  s  bath  yields  equally  good  results.  It  consists  of  a 
solution  of  equal  parts  of  tin-salt  and  common  salt  in  rain- 
water. The  manipulation  is  the  same  as  given  above. 

A  durable  coating  of  tin  is  also  produced  with  the  use  of 
potassium  stannate,  which  is  prepared  as  follows  :  Tin  is  melted 
and  then  granulated  by  pouring  it  into  water.  The  granulated 
tin  is  brought  into  a  vessel  of  glass  or  porcelain  and  crude  nitric 
acid  poured  over  it,  whereby,  with  strong  effervescence  of  the 
fluid  and  the  evolution  of  brown-red  vapors,  it  is  converted  into 
a  white  powder  consisting  of  stannic  oxide.  The  latter  is  sep- 
arated from  the  unchanged  tin  by  washing  with  water,  and 
dried.  The  dry  powder  is  mixed  with  pure  potash  in  the  pro- 
portion of  3  parts  stannic  oxide  and  4  parts  potash.  The 
mixture  is  melted  in  an  iron  crucible  and  the  fused  mass  poured 
upon  a  stone  slab.  It  consists  of  potassium  stannate  and  is 
dissolved  in  boiling  water.  Potassium  stannate  may  also  be 
prepared  by  adding  to  a  solution  of  tin-salt  in  water  aqua  am- 
monia as  long  as  a  precipitate  is  formed.  The  mass  is  then 
allowed  to  drain  off  upon  a  linen  cloth  and  repeatedly  washed 
with  water.  The  residue,  consisting  of  stannous  hydrate,  is 
boiled  with  strong  potash  lye,  and  the  solution  of  potassium 
stannate  thus  obtained  diluted  with  water. 

The  tinning  of  needles  is  effected  by  spreading  them  out  upon 
a  sieve  and  immersing  the  latter  in  the  bath ;  larger  articles  are 
touched  with  a  tin-rod  while  in  the  bath.  The  temperature  of 
the  bath  should  be  between  122°  and  212°  F.  Larger  articles 


DEPOSITION    OF   TIN,  ZINC,  LEAD,  AND    IRON.  333 

of  brass  or  bronze  are  best  coppered  previous  to  tinning,  which 
is  effected  by  wrapping  them  with  iron  wire  and  immersing  them 
in  dilute  sulphuric  acid  for  a  short  time  ;  hydrochloric  acid  may 
be  substituted  for  the  sulphuric  acid. 

Tinning  may  also  be  effected  by  dissolving  I  part  tin-salt  in 
10  parts  water,  adding  to  the  solution  one  of  2  parts  of  caustic 
potash  in  20  of  water  and  stirring  until  the  fluid  is  clear.  The 
articles  to  be  tinned  are  placed  upon  a  tin  plate.  The  latter  is 
brought  into  the  hot  bath  and  touched  on  several  places  with 
tin  rods. 

To  give  articles  of  brass,  copper,  or  iron  a  thin,  superficial 
coating  of  tin,  dip  them  in  a  solution  of  tin-salt  in  which  granu- 
lated tin  has  been  lying  for  some  time,  then  dust  them  with  tin- 
powder,  rub  them  with  a  woollen  rag,  and  repeat  the  operation 
until  the  article  appears  tinned. 

A  characteristic  method  of  tinning  by  Stolba  is  as  follows : 
Prepare  a  solution  of  1.75  ozs.  of  tin-salt  and  5.64  drachms  of 
pulverized  tartar  in  one  quart  of  water ;  moisten  with  this  solu- 
tion a  small  sponge  and  dip  the  latter  into  pulverulent  zinc. 
By  then  rubbing  the  thoroughly-cleansed  and  pickled  articles 
with  the  sponge  they  imediately  become  coated  with  a  film  of 
tin.  To  obtain  uniform  tinning,  the  sponge  must  be  repeatedly 
dipped  now  into  the  solution  and  then  into  the  zinc-powder, 
and  the  rubbing  continued  for  a  few  minutes. 

For  coloring  and  platinizing  tin,  see  special  chapter. 

2.  Deposition  of  Zinc. 

Properties  of  zinc. — Zinc  is  a  bluish-white  metal,  possessing 
high  metallic  lustre.  It  melts  at  776°  F.  At  the  ordinary 
temperature  zinc  is  brittle,  but  it  is  malleable  at  between  212° 
and  300°  F.,  and  can  be  rolled  into  sheets;  at  392°  F.  it  again 
becomes  brittle  and  may  be  readily  reduced  to  powder.  The 
specific  gravity  of  zinc  varies  from  about  6.86  to  7.2.  When 
strongly  heated  in  the  air  or  in  oxygen  it  burns  with  a  greenish- 
white  flame,  producing  dense  white  fumes  of  the  oxide. 

In  moist  air  it  becomes  coated  with  a  thin  layer  of  basic  car- 


334          ELECTRO- DEPOSITION  OF  METALS. 

bonate,  which  protects  the  metal  beneath  from  further  oxida- 
tion. Pure  zinc  dissolves  slowly  in  the  ordinary  mineral  acids, 
but  the  commercial  article  containing  foreign  metals  is  rapidly 
attacked,  with  evolution  of  hydrogen. 

Zinc  being  a  very  electro-positive  metal,  precipitates  most  of 
the  heavy  metals  from  their  solutions,  especially  copper,  silver, 
lead,  antimony,  arsenic,  tin,  cadmium,  etc.,  this  being  the  reason 
why  in  dissolving  impure  zinc  the  admixed  metals  do  not  pass 
into  solution  so  long  as  zinc  in  excess  is  present.  Caustic 
alkalies  also  dissolve  zinc  with  formation  of  an  oxide  and  free 
hydrogen,  especially  when  it  is  in  contact  with  a  more  electro- 
negative metal. 

Zinc  in  contact  with  iron  protects  the  latter  from  rust,  and 
also  prevents  copper  from  dissolving  when  in  contact  with  it. 

Zinc  baths.  Although  most  metals  can  be  readily  plated 
with  a  thin,  firmly-adhering  layer  of  zinc,  experiments  to  pro- 
duce in  an  easy  and  convenient  manner,  upon  shaped  articles, 
really  uniform  thick  deposits  which  would  answer  all  require- 
ments, particularly  the  prevention  of  the  oxidation  of  iron, 
have  not  been  entirely  successful.  The  zinc  deposits  first  upon 
the  projecting  edges  and  portions  of  the  objects,  while  the  por- 
tions at  a  greater  distance  from  the  anodes  are  either  not  coated 
at  all  or  only  with  a  very  thin  film,  no  matter  whether  the  zinc 
bath  is  prepared  so  as  to  conduct  readily  or  not  readily.  In 
electro-zincking  smooth  sheet  iron  this  drawback  does  not 
make  itself  felt,  but,  on  the  other  hand,  the  fact  that  with  the 
most  suitable  current-strength  for  a  normal  and  homogeneous 
deposit  the  latter  is  formed  too  slowly,  is  an  obstacle  to  the 
substitution  of  electro-zincking  for  the  ordinary  process  of  gal- 
vanizing. Numerous  exhaustive  experiments  have  been  made 
to  produce  in  a  practicable  manner  and  in  a  short  time  a  zinc- 
deposit  of  sufficient  thickness  upon  iron,  and  while  some  of 
these  experiments  were  successful  in  so  far  that  zinc  deposits 
were  produced  which,  as  regards  thickness  and  density,  were 
not  only  equal,  but  superior  to  those  by  the  ordinary  galvaniz- 
ing method,  the  cost  considerably  exceeded  that  of  the  latter 
process. 


DEPOSITION    OF   TIN,  ZINC,  LEAD,  AND    IRON.  335 

Better  results  are  obtained  in  zincking  articles  with  depres- 
sions by  depositing  not  pure  zinc  but  zinc  in  combination  with 
other  metals.  In  doing  this,  of  course,  zinc  must  be  present 
largely  in  excess  if  the  deposit  is  to  have  the  effect  of  pure 
zinc  in  protecting  the  plated  article  from  rust.  By  the  addi- 
tion of  salts  of  magnesium  and  aluminium  to  the  zinc  bath, 
Schaag  and  others  have  endeavored  to  deposit  zinc  with  a  con- 
tent of  these  metals.  While  the  possibility  of  depositing  alu- 
minium from  aqueous  solutions  is  doubtful,  it  is  very  likely 
that  in  Schaag's  patented  process  neither  the  magnesium  nor 
the  aluminium  is  the  effective  agent,  but  the  tin  or  mercury, 
salts  of  which,  Schaag  also  adds  to  the  zinc  bath.  But  such 
additions  are  nothing  new,  since  deposits  of  zinc-tin  alloys  with 
and  without  mercury  salts  have  for  many  years  been  produced. 
The  same  effect  is  produced  by  an  addition  of  tin  and  nickel 
to  the  zinc  bath,  and  experiments  have  conclusively  shown  that 
deposits  upon  iron  produced  in  such  a  bath  protect  the  iron 
from  rust  as  well  as  a  deposit  of  pure  zinc. 

Below  the  pure  zinc  baths  mostly  used  are  given  : 

I.  Sulphate  of  zinc  (white  vitriol)  2.8  ozs.,  ammonium  sul- 
phate I  y^  ozs.,  sal  ammoniac  1 1  drachms,  water  I  quart.     Dis- 
solve the  salts  in  the  heated  water  and  use  the  bath  at  68°  F. 
The  current-strength  should  only  be  slightly  greater  than  nec- 
essary for  the  decomposition  of  the  bath ;    the  current  of  two 
Bunsen  elements  coupled  one  after  the  other  is  quite  too  strong, 
and    must,    therefore,    be    correspondingly    weakened    by    the 
resistance-board. 

As  anodes,  rolled  zinc  sheets  of  not  too  small  dimensions  are 
to  be  used.  This  bath  is  suitable  for  heavily  zincking  objects 
(sheets  and  plates)  of  wrought-  and  cast-iron,  steel,  and  all 
other  metals,  but  not  for  zincking  hollow  articles  if  anodes  can- 
not at  equal  distances  be  placed  around  them.  The  most  suit- 
able tension  is  2.8  to  3  volts. 

II.  Caustic  potash  2  ozs.,  chloride  of  zinc  5*^  drachms,  sal 
ammoniac   II    drachms,  water   I    quart.     Dissolve  the  caustic 
potash   in  one-half  of  the  water,  and  the  chloride  of  zinc  and 


ELECTRO-DEPOSITION   OF   METALS. 

sal  ammoniac  in  the  other  half,  and  mix  the  solution  with 
stirring.  The  result  is  a  clear  fluid  which  requires  a  current  of 
2.5  to  3  volts  for  its  decomposition.  Zinc  sheets  are  also  used 
as  anodes.  In  this  bath  the  deposit  upon  hollow  objects  pro- 
ceeds better  than  in  the  preceding,  though  frequent  turning  of 
the  articles  is  necessary. 

III.  Alum   3^   ozs.,  hydrated  oxide  of   zinc   5^   drachms, 
water   I  quart.     Dissolve   14  drachms  of  sulphate  of  zinc  in  i 
pint  of  water,  and  carefully  add  potash  lye  until  a  further  drop 
of   it  no  longer  produces  a  precipitate.     Since  potash  lye  dis- 
solves the  hydrated  oxide  of  zinc,  an  excess  has  to  be  avoided. 
The  precipitate  is  filtered  off,  washed  with  water,  and  the  hy- 
drated oxide  of  zinc,  while  still  moist,  is  heated  together  with 
the  solution  of  3^  ozs.  of  alum  in  I  quart  of  water,  whereby  it 
is  completely  dissolved.     This  bath  requires  a  current  of  3  to 
3.5  volts. 

IV.  Sulphate  of  zinc  (white  vitriol)  2.8  ozs.,  water  I   quart, 
and  potash  lye  sufficient  to  redissolve  the  precipitated  hydrated 
oxide  of  tin.     This  bath   also  works  quite  well,  and   requires 
from  2.75  to  3  volts  and  1.5  amperes  per  15  j£  square  inches. 

Solution  of  cyanide  of  zinc  in  potassium  cyanide  may  also 
be  used  for  zincking,  such  a  bath  having  been  warmly  recom- 
mended by  some  authors.  However,  the  production  of  deposits 
of  some  thickness  requires  a  long  time,  and  the  deposit  itself 
shows  a  tendency  to  peel  off. 

Execution  of  zincking.  Next  to  thorough  cleansing  and 
pickling  the  objects,  especially  iron  castings,  and  regulating 
the  current,  electro-zincking  depends  on  the  frequent  turning 
and  changing  of  the  objects  in  the  bath,  since  the  deposit  is 
chiefly  formed  upon  the  portions  nearest  to  the  anodesT  and 
not  at  all,  or  with  difficulty,  upon  the  portions  away  from  the 
anodes.  If,  notwithstanding  frequent  changing,  some  portions 
do  not  acquire  a  deposit,  recourse  must  be  had,  as  in  nickeling, 
to  the  hand  anode.  Next  to  frequently  changing  the  articles 
in  the  bath,  it  is  recommended  to  scratch-brush  them  several 
times,  especially  if  heavy  deposits  are  to  be  produced.  It  is 
also  advisable  to  somewhat  heat  the  baths,  if  possible. 


DEPOSITION   OF  TIN,  ZINC,  LEAD,  AND    IRON.  337 

It  is  of  advantage  to  superficially  zinc  iron  objects  by  a  com- 
bined process  of  contact  and  boiling,  and  then  to  augment  the 
layer  of  zinc  in  the  bath. 

After  thorough  scratch-brushing  with  a  steel  brush,  not  too 
hard,  and  a  decoction  of  soap-root,  the  zincked  objects  are 
rinsed  in  lime-water,  then  plunged  into  hot  water,  and  dried 
in  saw-dust ;  polishing  is  effected  upon  soft  cloth  bobs  with 
Vienna  lime  and  oil. 

For  zincking  iron  by  contact  quite  a  concentrated  solution  of 
chloride  of  zinc  and  sal  ammoniac  in  water,  only,  is  suitable,  in 
which  the  objects  are  placed  in  contact  with  large  surfaces  of  zinc. 

To  coat  brass  and  copper  with  a  bright  layer  of  zinc  proceed 
as  follows  :  Boil  commercial  zinc-gray,  i.  e.,  very  finely-divided 
metallic  zinc,  several  hours  with  concentrated  solution  of  caus- 
tic soda.  Then  immerse  the  articles  to  be  zincked  in  the  boil- 
ing fluid,  when,  by  continued  boiling,  the  articles  will  in  a  short 
time  become  coated  with  a  very  bright  layer  of  zinc.  When  a 
copper  article  thus  coated  with  zinc  is  carefully  heated  in  an 
oil  bath  to  between  248°  and  284°  F.,  the  zinc  alloys  with  the 
copper,  forming  a  sort  of  bronze  similar  to  tombac. 

Weil  zincks  copper  and  coppered  objects  by  immersing  them 
in  a  boiling  concentrated  solution  of  caustic  potash  in  contact 
with  zinc.  The  coating  thus  obtained  is  said  to  be  adherent 
and  brilliant. 

For  coloring  and  platinizing  zinc,  see  special  chapter. 

Zinc  alloys. — The  production  of  the  principal  zinc  alloy, 
brass,  by  the  galvanic  method,  having  already  been  mentioned, 
and  also  that  of  a  zinc-nickel-copper  alloy  (German  silver),  it 
remains  to  give  an  alloy  of  zinc  with  tin,  or  of  zinc,  tin  and 
nickel,  which  can  be  produced  by  the  use  of  the  battery. 

A  suitable  bath  for  depositing  this  alloy  consists  of:  Chloride 
of  zinc  6^  drachms,  crystallized  stannous  chloride  9  drachms, 
pulverized  tartar  9  drachms,  pyrophosphate  of  soda  2  ^  drachms, 
water  I  quart.  Dissolve  the  salt  at  a  boiling  heat,  and  filter 
the  cold  solution,  when  it  is  ready  for  use.  For  anodes,  cast 
plates  of  equal  parts  of  tin  and  zinc  are  used. 
22 


33 8  ELECTRO-DEPOSITION    OF   METALS. 

These  deposits  have  no  special  advantages,  but,  on  the  other 
hand,  a  deposit  containing  zinc  in  large  excess  has  the  same  ef- 
fect of  protecting  iron  from  rust  as  a  deposit  of  pure  zinc. 

By  preparing  a  bath  which  contains  as  conducting  salt  sodium 
citrate,  and  ammonium  chloride,  and  the  chlorides  of  the  metals 
in  the  proportion  of  4  zinc  chloride  to  I  tin  chloride,  a  deposit 
is  obtained  which  not  only  is  a  perfect  protection  against  rust, 
but  also  enters  far  better  into  depressions  than  pure  zinc.  By 
adding  to  the  bath  a  small  quantity  of  chloride  of  mercury  or  of 
nickel,  alloys  of  zinc,  tin  and  mercury  or  of  zinc,  tin  and  nickel 
are  formed  which  are  distinguished  from  pure  zinc  deposits  by 
a  finer  structure. 

3.  Deposition  of  Lead. 

The  properties  of  lead  only  interest  us  in  so  far  as  it  being 
less  attacked  by  most  mineral  acids  than  other  metals,  objects 
have  been  coated  with  it  in  order  to  protect  them  against  the 
action  of  such  agents.  For  decorative  purposes  electro- 
deposits  of  lead  are  not  used,  and  those  as  a  protection  against 
chemical  influences  cannot  be  produced  of  sufficient  thickness 
for  that  purpose. 

Lead  baths. — I.  Dissolve,  by  continued  boiling,  caustic  potash 
1.75  ozs.  and  finely  pulverized  litharge  0.17  oz.  in  I  quart  of 
water. 

II.  According  to  Watt,  the  following  solution  is  used : 
Acetate  of  lead  0.17  oz.,  acetic  acid  0.17  oz.,  water  I  quart. 

The  bath  prepared  according  to  formula  I.  deserves  the 
preference. 

Lead  baths  require  anodes  of  sheet- lead  or  cast-lead  plates, 
a  very  weak  current,  and  in  order  to  produce  a  dense  deposit 
of  some  thickness,  the  objects  have  to  be  frequently  scratch- 
brushed.  Iron  is  best  previously  coppered.  Superoxide  of 
lead  being  separated  upon  the  anodes,  they  have  to  be  fre- 
quently cleansed  with  a  scratch-brush.  The  formation  of 
superoxide  of  lead  is  utilized  for  the  production  of  the  so- 
called  Nobili's  rings  (electrochromy),  which  will  be  mentioned 
below. 


DEPOSITION    OF   TIN,  ZINC,  LEAD,  AND    IRON.  339 

To  coat  gun  barrels  and  other  articles  of  steel  or  iron  with 
superoxide  of  lead  as  a  protection  against  rust,  suspend  the 
bright  articles  as  anodes  in  a  solution  of  nitrate  of  lead  mixed 
with  ammonium  nitrate. 

Leading  by  contact  is  effected  by  suspending  the  objects, 
previously  thoroughly  freed  from  grease,  in  the  boiling  solution 
prepared  according  to  formula  L,  in  contact  with  a  piece  of 
tin. 

Metallic  chromes  (Nobili's  rings,  iridescent  colors,  electro- 
chromy.)  The  separation  of  superoxide  of  lead  upon  the 
anodes  or  upon  objects  suspended  as  anodes,  produces  superb 
effects  of  colors.  For  the  production  of  such  colors,  a  bath  is 
prepared  by  boiling  for  half  an  hour  3  J^  ozs.  of  caustic  potash, 
14  drachms  of  litharge,  and  I  quart  of  water.  The  operation 
is  as  follows :  Suspend  the  articles,  carefully  freed  from  grease 
and  pickled,  to  the  anode-rods,  and  with  a  weak  current  intro- 
duce in  the  lead  solution  a  thin  platinum  wire  connected  with 
the  object-rod  by  flexible  copper  wire,  without,  however,  touch- 
ing the  article.  The  latter  will  successively  become  colored 
with  various  shades — yellow,  green,  red,  violet,  and  blue.  By 
the  continued  action  of  the  current,  these  colors  pass  into  a 
discolored  brown,  which  also  appears  in  the  beginning  if  the 
current  is  too  strong,  or  the  platinum  wire  be  immersed  too 
deep.  Such  unsuccessful  coloration  has  to  be  removed  by 
rapidly  dipping  in  aqua  fortis,  and,  after  rinsing  in  water,  sus- 
pending the  article  in  the  bath.  For  coloring  not  too  large 
surfaces,  a  medium-sized  Bunsen  element  is,  as  a  rule,  sufficient, 
if  the  platinum  wire  be  immersed  about  ^  inch. 

Colors  of  all  possible  beautiful  contrasts  may  be  obtained  by 
perpendicularly  placing  between  the  objects  to  be  colored  and 
the  platinum  wire  a  piece  of  stout  parchment  paper,  or  pro- 
viding the  latter  with  many  holes  or  radial  segments. 

Another  process  of  producing  these  effects  of  colors  is  as 
follows:  Prepare  a  concentrated  solution  of  acetate  of  lead 
(sugar  of  lead),  and  after  being  filtered,  pour  it  into  a  shallow 
porcelain  dish.  Then  immerse  a  plate  of  polished  steel  in  the 


340  ELECTRO-DEPOSITION    OF   METALS. 

solution,  and  allow  it  to  rest  upon  the  bottom  of  the  dish. 
Now  connect  a  small  disc  of  sheet  copper  with  the  wire  proceed- 
ing from  the  zinc  element  of  a  constant  battery  of  two  or  three 
cells,  the  wire  connected  with  the  copper  element  being  placed 
in  contact  with  the  steel  plate.  If  now  the  copper  disc  be 
brought  as  close  to  the  steel  plate  as  possible  without  touching 
it,  in  a  few  moments  a  series  of  beautiful  prismatic  colorations 
will  appear  upon  the  steel  surface,  when  the  plate  should  be 
removed  and  rinsed  in  clean  water.  These  colorations  are 
films  of  lead  in  the  state  of  peroxide,  and  the  varied  hues  are 
due  to  the  difference  in  thickness  of  the  precipitated  peroxide 
of  lead,  the  light  being  reflected  through  them  from  the  pol- 
ished metallic  surface  beneath.  By  reflected  light  every  pris- 
matic color  is  visible,  and  by  transmitted  light  a  series  of  pris- 
matic colors  complementary  to  the  first  colors  will  appear 
occupying  the  place  of  the  former  series.  The  colors  are  seen 
to  the  greatest  perfection  by  placing  the  plate  before  a  window 
with  the  back  to  the  light,  and  holding  a  piece  of  white  paper 
at  such  an  angle  as  to  be  reflected  upon  its  surface.  The 
colorations  are  not  of  a  fugitive  character,  but  will  bear  a  con- 
siderable amount  of  friction  without  being  removed.  In  proof 
of  the  lead  oxide  being  deposited  in  films  or  layers,  it  may  be 
stated  that  if  the  deposit  be  allowed  to  proceed  a  few  seconds 
beyond  the  time  when  its  greatest  beauties  are  exhibited,  the 
coloration  will  be  less  marked,  and  become  more  or  less  red, 
green  or  brown.  If  well  rubbed,  when  dry,  with  the  finger  or 
fleshy  part  of  the  hand,  a  rich  blue  colored  film  will  be  laid 
bare  by  the  removal  of  the  delicate  film  above  it. 

The  plan  recommended  by  Mr.  Gassiot  to  obtain  the  metallo- 
chrdmes  is  to  place  over  the  steel  plate  a  piece  of  card  cut 
into  some  regular  device,  and  over  this  a  rim  of  wood,  the 
copper  disc  being  placed  above  this.  Very  beautiful  effects 
are  obtained  when  a  piece  of  fine  copper  wire  is  turned  up  in 
the  form  of  a  ring,  star,  cross  or  other  pattern,  and  connected 
with  the  positive  electrode,  this  being  in  fact  one  of  the  simplest 
and  readiest  methods  of  obtaining  the  colorations  upon  the 


DEPOSITION   OF  TIN,  ZINC,  LEAD,  AND    IRON.  341 

polished  metal.  Metallo-chromy  is  extensively  employed  in 
Nuremberg  to  ornament  metallic  toys.  It  has  been  adopted 
in  France  for  coloring  bells,  and  in  Switzerland  for  coloring 
the  hands  and  dials  of  watches.  In  using  the  lead  solutions  to 
produce  metallic  chromes,  it  must  be  remembered  that  me- 
tallic lead  becomes  deposited  upon  the  cathode,  consequently 
the  solutions  in  time  become  exhausted,  and  must  therefore  be 
renewed  by  the  addition  of  the  lead  salt. 

4.  Deposition  of  Iron  (Steeling). 

The  principal  practical  use  of  the  electro-deposition  of  iron 
is  to  cover  printing  plates  of  softer  metals  with  a  coating  of 
"  steel,"  to  increase  their  wearing  qualities.  The  steeling  of 
printing  plates,  however,  has  no  advantage  over  nickeling  or 
cobalting,  which  has  been  introduced  with  the  best  success. 

Steel  baths. — I.  According  to  Varrentrapp :  Pure  green 
vitriol  43^  ozs.,  sal  ammoniac  3^  ozs.,  water  I  quart.  Boil 
the  water  for  */2  hour  to  remove  all  air,  and,  after  cooling,  add 
the  green  vitriol  and  sal  ammoniac.  By  the  action  of  the  air, 
and  the  oxygen  appearing  on  the  anodes,  this  bath  is  readily 
decomposed,  insoluble  basic  sulphate  of  iron  being  separated 
as  a  delicate  powder,  which  has  to  be  frequently  removed 
from  the  fluid  by  filtering.  To  decrease  decomposition,  the 
double  sulphate  of  iron  and  ammonium,  which  can  be  more 
readily  obtained  pure  and  free  from  oxide,  may  be  used. 

II.  Sal  ammoniac  3^  ozs.,  water  I  quart.  This  neutral 
solution  of  sal  ammoniac  may  be  made  into  an  iron  bath  by 
hanging  in  it  iron  sheets  as  anodes,  suspending  an  iron  or 
copper  plate  as  cathode,  and  allowing  the  current  to  circulate 
until  a  regular  separation  of  iron  is  attained,  which  is  generally 
the  case  in  5  to  6  hours.  Although  a  separation  of  hydrated 
oxide  of  iron  also  takes  place  in  this  bath,  it  is  in  a  less  degree 
than  in  that  prepared  according  to  formula  I.  For  the  pro- 
duction of  not  too  heavy  a  deposit  of  iron,  some  operators  claim 
to  have  obtained  the  best  results  with  this  bath. 

According  to  Boettger  the  following  bath  serves  for  steeling : 


342  ELECTRO-DEPOSITION   OF   METALS. 

III.  Potassium   ferrocyanide    (yellow    prussiate    of    potash) 
0.35  oz.,  Rochelle  salt  0.7  oz.,  distilled  water  200  cubic  centi- 
meters.    To  this  solution  is  added  a  solution  of  1.69  drachms 
of  persulphate  of  iron  in  50  cubic  centimeters  of  water,  whereby  a 
moderate  separation  of  Berlin  blue  takes  place.     Then  add,  drop 
by  drop,  with  constant  stirring,  solution  of  caustic  soda  until 
the  blue  precipitate  has  disappeared.     The  clear  slightly  yellow- 
ish solution  thus  obtained  can  be  directly  used   for   steeling. 
This  bath  is  considered  excellent  for  coating  engraved  copper- 
plates with  iron. 

For  the  production  of  electrotypes  in  iron  the  following  baths 
(IV.  and  V.)  are  most  suitable:  — 

IV.  Ammonio-ferrous  sulphate  I  ^  ozs.,  water  I  quart.    The 
solution  must  be  kept  absolutely  neutral,  which  according  to 
Klein's  suggestion  is,  on  the  one  hand,  to  be  attained  by  the  use 
of  large  anode-surfaces,  and,  on  the  other,  by  suspending  in  the 
bath  a  copper  plate  and   connecting   it  with  the   anodes.     It 
would  seem  more  advantageous  to  maintain  the  neutrality  of 
the  bath  by  suspending  in  it  small  bags  filled  with  carbonate  of 
magnesia. 

V.  This  steel  bath  highly  recommended  by  Klein  consists  of 
a  solution  of  equal  parts  of  green  vitriol  and  sulphate  of  mag- 
nesia, which  is  kept  neutral  by  bags  filled  with  carbonate  of 
magnesia  suspended  in  the  fluid.     The  most  suitable  concentra- 
tion of  the  solution  corresponds  to  a  specific  gravity  of  1.55  ; 
and  according  to  the  most   recent  experiments,  the  current- 
density  should  at  the  utmost  amount  to  0.02  ampere  per  15  j£ 
square  inches,  with  a  distance  of  I  */2  inches  of  the  anodes  from 
the  plate,  this  distance  to  be  gradually  increased. 

For  steeling  his  copper  printing  plates,  which  are  frequently 
of  quite  large  dimensions,  C.  Obernetter,  of  Munich,  employs 
the  following  method:  The  plate  to  be  steeled  is  first  freed 
from  all  color,  which  is  best  effected  by  means  of  chloroform  or 
oil  of  turpentine.  It  is  then  thoroughly  washed  and  brushed 
by  means  of  a  bristle-brush  with  potash  lye  or  a  solution  of  I 
part  potassium  cyanide  in  20  parts  water,  and  again  washed.  • 


DEPOSITION   OF   TIN,  ZINC,  LEAD,  AND   IRON.  343 

In  this  state  the  plate  is  suspended  to  the  cathode  of  the  steel- 
ing bath.  A  clean  steel  plate  serves  as  anode.  Both  the 
anode  and  cathode  are  in  a  horizontal  position.  Bubbles  form- 
ing on  the  cathode  are  readily  removed  by  means  of  a  feather. 
In  about  five  minutes  the  plate  is  thoroughly  steeled. 

The  iron  bath  consists,  according  to  Obernetter,  of  ferrous 
sulphate  30  parts  by  weight,  iron-alum  30,  sal  ammoniac  60, 
dissolved  in  warm  distilled  water  1000. 

The  solution  is  allowed  to  stand  for  two  days,  and  is  then 
filtered  twice.  It  should  also  be  filtered  every  time  before  use. 

After  steeling,  the  plate  is  cleansed  in  the  above  described 
manner,  and  oiled  to  prevent  rusting. 

When  during  the  operation  of  printing  the  deep  places  of  the 
plate  commence  to  become  red,  i.  e.,  when  the  copper  shines 
through,  the  steeled  plate  may  be  re-steeled,  but,  according  to 
Obernetter,  this  should  not  be  done  more  than  once.  It  is  best 
in  every  case  to  first  remove  the  old  steeling  with  dilute  sul- 
phuric or  nitric  acid,  and  then  to  re-steel  the  plate. 

According  to  Obernetter's  statements,  21,000  copies  were 
printed  from  a  plate  thus  steeled  without  the  plate  suffering 
any  injury,  the  last  impression  being  in  every  respect  equal  to 
the  first. 

For  decorative  purposes,  a  deep  black  deposit  of  iron  may, 
according  to  uLa  Melallurgie,"  be  produced  as  follows:  Dis- 
solve as  large  a  quantity  of  steel  filings  as  possible  in  50  quarts 
of  commercial  hydrochloric  acid.  The  saturation  of  the  solu- 
tion is  recognized  by  a  sediment,  which  no  longer  dissolves, 
being  formed  on  the  bottom  of  the  vessel.  Then  add  2  Ibs.  of 
white  arsenic,  and  vigorously  stir  the  mixture.  The  arsenic 
dissolves  very  slowly,  but  the  bath  cannot  be  considered  fin- 
ished until  all  of  it  is  dissolved,  and  the  color  obtained  by  means 
of  the  bath  is  the  deeper  the  more  complete  the  solution  of  the 
arsenic.  The  articles  to  be  treated  are  connected  to  the  nega- 
tive pole  of  the  battery,  iron  and  carbon  plates  serving  as 
anodes.  For  a  bath  of  50  quarts,  two  Bunsen  elements  about 
7^4  inches  high  are  required,  and  the  bath  being  very  acid,  the 


344  ELECTRO-DEPOSITION   OF   METALS. 

articles  must  be  connected  with  the  battery  prior  to  immersion. 
Upon  copper  and  brass  the  deposit  is  directly  produced,  but 
iron  articles  being  attacked  by  the  bath,  are  first  provided  with 
a  coat  of  nickel.  The  deposit  of  iron  upon  this  nickel  coating 
is  very  beautiful,  and  has  been  designated  as  "  black  nickel- 
ling."  The  coating  must,  of  course,  be  protected  from  oxida- 
tion by  a  colorless  lacquer. 

Management  of  iron  baths. — As  previously  mentioned,  the 
insoluble  precipitate  from  time  to  time  formed  in  the  bath  has 
to  be  removed  by  filtration.  This  precipitate  is,  however, 
very  delicate, 'and  when  stirred  up  might  settle  upon  the  ob- 
jects and  prevent  the  adherence  of  the  deposit.  It  is,  therefore, 
advisable  to  use  for  steel  baths,  vats  of  much  greater  depth 
than  correspond  to  the  height  of  the  objects,  whereby  the 
stirring  up  of  the  sediment  in  suspending  the  objects  in  the 
bath  is  best  avoided.  The  baths  must  be  kept  thoroughly 
neutral,  which  may  be  effected  in  various  ways.  One  method 
has  already  been  mentioned  in  connection  with  formula  IV. ; 
another  method,  which  has  been  used  with  decided  success, 
consists  in  precipitating,  excluding  the  air  as  much  as  possible, 
a  solution  of  pure  green  vitriol  with  ammonium  carbonate, 
quickly  filtering  off  the  ferrous  carbonate,  washing  the  latter 
once  or  twice  in  cold  water  previously  boiled,  stirring  it  while 
moist  into  the  bath,  and  allowing  it  to  settle  for  one  hour. 

Execution  of  steeling. — Only  the  manipulations  for  the  pro- 
duction of  thin  deposits  will  here  be  discussed.  The  production 
of  heavy  galvanoplastic  deposits  of  iron  will  be  explained  later 
on  under  "  Galvanoplasty." 

The  clean  and  pickled  objects  are  coated  in  the  baths  ac- 
cording to  formulae  I.  and  II.  with  a  current  of  I  to  1.25  volts, 
and  the  anodes  at  a  distance  of  3^  to  4^  inches,  after  which 
the  current  is  reduced  to  0.75  or  i  volt.  To  produce  iron  de- 
posits of  any  kind  of  thickness,  the  escape  of  the  hydrogen 
bubbles  which  settle  on  the  objects  must  be  promoted  by 
frequent  blows  with  the  finger  upon  the  object-rod.  As  anodes, 
iron  sheets  of  a  large  surface  freed  from  scale  by  pickling  are 


DEPOSITION    OF   ANTIMONY,  ARSENIC,  ALUMINIUM.         345 

to  be  used.  When  steeling  is  finished,  the  articles  are  thor- 
oughly rinsed,  then  plunged  into  very  hot  water,  and,  after 
drying  in  sawdust,  placed  for  several  hours  in  a  drying  cham- 
ber heated  to  about  212°  F.,  to  expel  all  moisture  from  the 
pores. 

Steeling  by  contact  is  readily  effected  by  touching  the  objects 
with  zinc,  best  in  a  bath  prepared  according  to  formula  I. 


CHAPTER  XIII. 

DEPOSITION   OF   ANTIMONY,  ARSENIC,  ALUMINIUM. 

I.  Deposition  of  Antimony. 

Properties  of  Antimony. — Electro- deposited  antimony  pos- 
sesses a  gray  lustre,  while  native,  fused  antimony  shows  a 
silver-white  color.  Antimony  is  hard,  very  brittle,  and  may 
easily  be  reduced  to  powder  in  a  mortar.  It  melts  at  842°  F., 
and  at  a  strong  red  heat  takes  fire  and  burns  with  a  white  flame, 
forming  the  trioxide.  Its  density  is  6.8.  It  is  permanent  in  the 
air  at  ordinary  temperatures.  Cold,  dilute,  and  concentrated 
sulphuric  acid  have  no  effect  upon  antimony,  but  the  hot  con- 
centrated acid  forms  sulphide  of  antimony.  By  nitric  acid  the 
metal  is  more  or  less  energetically  oxidized,  according  to  the 
strength  and  temperature  of  the  acid. 

Antimony  baths. — Electro-depositions  of  antimony  are  but  sel- 
dom made  use  of  in  the  industries,  though  they  are  very  suit- 
able for  the  production  of  contrasts  in  decorating.  Gore  dis- 
covered the  explosive  power  of  depositions  of  antimony  chloride, 
or  of  antimony  containing  hydrochloric  acid.  According  to 
Gore,  a  bath  consisting  of  tartar  emetic  3  ozs.,  hydrochloric 
acid  4j^  ozs.,  tartaric  acid  3  ozs.,  and  water  I  quart,  yields  a 
gray  crystalline  deposit  of  antimony.  This  bath  requires  a 
current  of  about  3  volts.  The  deposit  possesses  the  property 
of  exploding  when  scratched  with  a  hard  object.  The  explo- 


ELECTRO- DEPOSITION    OF   METALS. 

sion  of  the  deposit  is  caused  by  a  content  of  chloride  of  anti- 
mony. Bottger  found  3  to  5  per  cent,  of  chloride  of  antimony 
in  the  deposit,  and  Gore  6  per  cent.  A  similar  explosive  de- 
posit is  obtained  by  electrolyzing  a  simple  solution  of  chloride 
of  antimony  in  hydrochloric  acid  (liquid  butter  of  antimony, 
liquor  stibii  chlorati]  with  the  current. 

A  lustrous  non-explosive  deposit  of  antimony  is  obtained  by 
boiling  4.4  ozs.,  of  carbonate  of  potash,  2.1 1  ozs.,  of  pulverized 
antimony  sulphide,  and  I  quart  of  water,  for  I  hour,  replacing 
the  water  lost  by  evaporation,  and  filtering.  Use  the  bath 
boiling  hot,  employing  cast  antimony  plates  or  platinum  sheets 
as  anodes. 

Another  antimany  bath  may  be  prepared  by  dissolving  freshly 
precipitated  sulphide  of  antimony  with  an  excess  of  sulphide  of 
ammonia.  It  yields  a  very  lustrous  and  adherent  deposit  of 
antimony,  which,  in  6  to  8  minutes,  is  of  sufficient  thickness  to 
bear  polishing  with  Vienna  lime  upon  rapidly  revolving  cloth 
wheels.  An  unpleasant  feature  of  this  bath  is  that  during  the 
plating  process  much  sulphur  is  separated,  which  renders  the 
bath  turbid,  so  that  it  has  to  be  frequently  filtered.  With  the 
use  of  platinum  anodes,  this  separation  of  sulphur  is,  of  course, 
still  greater  than  with  antimony  anodes. 

2.  Deposition  of  Arsenic. 

Properties  of  arsenic. — Arsenic  has  a  gray-white  color,  a 
strong  metallic  lustre,  is  very  brittle,  and  evaporates  at  a  red 
heat.  In  dry  air  arsenic  retains  its  lustre,  but  soon  turns  dark 
in  moist  air.  It  is  scarcely  attacked  by  dilute  hydrochloric 
and  sulphuric  acids,  while  concentrated  sulphuric  acid  as  well 
as  nitric  acid  oxidizes  it  to  arsenious  acid.  If  caustic  alkalies 
are  fused  together  with  arsenic,  a  portion  of  the  latter  is  con- 
verted into  alkaline  arsenate. 

Arsenic  baths. — Deposits  of  arsenic  are  more  frequently 
used  than  antimony  deposits  for  decorative  purposes ;  for  in- 
stance, to  color  gray  the  dead  background  of  brassed  lamp- 
legs,  vases,  etc.,  while  the  prominent  portions  are  bright  brass. 


DEPOSITION    OF   ANTIMONY,  ARSENIC,  ALUMINIUM.          347 

A   solution   suitable  for   depositing  arsenic  upon  all  kinds  of 
metals  is  as  follows : 

I.  Pulverized  arsenious  acid  I  ^  ozs.,  crystallized  pyrophos- 
phate  of  soda  0.7  oz.,  98  per  cent,  potassium  cyanide  I  ^  ozs., 
water  I  quart. 

Dissolve  the  pyrophosphate  of  soda  and  the  potassium  cyanide 
in  the  cold  water,  and  after  adding,  with  stirring,  the  arsenious 
acid,  heat  until  the  latter  is  dissolved.  In  heating,  fumes  con- 
taining prussic  acid  escape,  the  inhalation  of  which  must  be 
carefully  avoided.  The  bath  is  used  warm,  and  requires  a 
vigorous  current  of  at  least  4  volts,  so  that,  at  the  least,  3 
Bunsen  elements  have  to  be  coupled  for  tension.  After  sus- 
pending the  objects  they  are  first  colored  black-blue,  the 
color  passing  with  an  increased  thickness  of  the  deposit  into 
pale  blue,  and  finally  into  the  true  arsenic  gray.  Platinum 
sheets  or  carbon  plates  are  to  be  used  as  anodes. 

Instead  of  a  bath  prepared  according  to  formula  I.,  a  solu- 
tion of  the  following  composition  may  be  used:  — 

II.  Sodium  arsenate  I  ^  ozs.,  98  per  cent,  potassium  cyanide 
0.8  oz.,  water  I  quart.     Boil  the  solution  for  half  an  hour,  then 
filter  and  use  it  at  a  temperature  of  at  least   167°  to  176°  F., 
with  a  strong  current ;  it  yields  a  good  deposit. 

Large  baths,  to  be  used  cold,  must  be  more  concentrated, 
and  require  a  stronger  current  than  hot  baths. 

When  the  baths  begin  to  work  irregularly  and  sluggishly, 
they  have  to  be  replaced  by  fresh  solutions. 

In  the  execution  of  deposits  of  arsenic  and  antimony  the 
same  rules  are  to  be  observed  as  for  the  other  electro-plating 
processes. 

Deposits  of  antimony  and  arsenic  by  contact  and  immersion 
are  much  used  for  coloring  brass  and  copper,  as  well  as  iron 
(browning  of  gun-barrels)  and  silver.  Most  frequently  a  warm 
solution  of  antimony  trichloride  (the  butter  of  antimony  of 
commerce)  in  hydrochloric  acid  is  used  for  this  purpose,  in 
which  the  clean  and  pickled  brass  articles  acquire  a  coating  of 
a  steel  gray  color  with  a  bluish  tinge.  By  using  instead  a  hot 


34^  ELECTRO-DEPOSITION   OF   METALS. 

mixture  of  chloride  of  arsenic  with  a  small  quantity  of  water,  a 
steel-gray  color  without  a  bluish  tinge  is  obtained. 

By  immersing  brass  in  a  solution  of  20  parts  by  weight  of 
arsenious  acid,  40  of  hydrochloric  acid,  800  of  water,  and  10  of 
sulphuric  acid  heated  to  between  122°  and  140°  F.,  it  becomes 
black  by  the  separation  of  pulverulent  arsenic ;  after  rinsing  in 
water  and  drying  the  coat  adheres  quite  well.  By  contact  with 
zinc  the  deposit  is  obtained  in  a  shorter  time  and  adheres 
better. 

3.  Deposition  of  Aluminium. 

Properties  of  aluminium. — Aluminium  is  a  white  silvery  metal 
with  an  almost  imperceptible  bluish  tinge.  It  is  extremely 
light,  the  specific  gravity  being  only  2.58,  is  very  malleable  and 
ductile,  takes  a  high  polish,  and  is  not  liable  to  tarnish  in  the 
air.  It  melts  at  about  I3OO°F.  Its  principal  common  impur- 
ities are  iron  and  silicon. 

Aluminium  does  not  seem  to  possess  any  qualities  which 
would  make  it  advantageous  as  an  electro-deposit  upon  other 
metals.  Many  solutions  have  been  proposed  which  it  was 
claimed  should  give  good  deposits  of  the  metal,  but,  on  trial, 
have  been  found  to  be  worthless.  The  solutions  given  below 
are  claimed  to  give  good  results,  but  are  here  mentioned  with 
due  reserve. 

Aluminium  baths. — I.  Bertrand  states  that  he  has  deposited 
aluminium  upon  a  plate  of  copper  in  a  solution  of  the  double 
chloride  of  aluminium  and  ammonium  by  using  a  strong  current 
from  three  Bunsen  elements,  the  bath  being  worked  at  140°  F. 

II.  Gaze's  process. — Mr.  Goze  obtained  a  deposit  of  alumin- 
ium by  the  single-cell  method  from  a  dilute  solution  of  the 
chloride.  The  liquid  was  placed  in  a  jar  in  which  was  im- 
mersed a  porous  cell  containing  dilute  sulphuric  acid ;  an 
amalgamated  zinc  plate  was  immersed  in  the  acid  solution  and 
a  plate  of  copper  in  the  chloride  solution,  the  two  metals  being 
connected  by  a  copper  conducting  wire.  At  the  end  of  some 
hours  the  copper  plate  became  coated  with  a  lead-colored  de- 


DEPOSITION    OF   ANTIMONY,  ARSENIC,  ALUMINIUM.         349 

posit  of  aluminium,  which,  when  burnished,  presented  the  same 
degree  of  whiteness  as  platinum  and  did  not  appear  to  tarnish 
readily  when  immersed  in  cold  water  or  exposed  to  the  atmos- 
phere, but  was  acted  upon  by  dilute  sulphuric  and  nitric  acids. 

III.  The  following  formula  is  given  by  Mr.  Herman  Reinbold, 
who  states  that  it  yields  excellent  results  :   Dissolve  50  parts  by 
weight  of  alum   in   300  of  water,  and   to  this  add   10   parts  of 
aluminium  chloride.     The  solution  is  to  be  heated  to  200°  F., 
and,  when  cold,  39  parts  of  potassium  cyanide  are  to  be  added. 
A  feeble  current  should  be  used. 

IV.  A  new  method  for  the  electro-deposition  of  aluminium  is 
as  follows:*  To  a  20  per  cent,  solution  of  ammonium-alum  in 
warm  water  add  a  solution  of  about  the  same  quantity  of  pearl- 
ash  and  of  a  small  quantity  of  ammonium  carbonate.     The  mix- 
ture effervesces  and  yields  a  precipitate,  which  is  filtered  off 
and  thoroughly  washed  with  water.     Over  the  precipitate  thus 
obtained  pour  a  warm  solution  of  16  per  cent,  ammonium-alum 
and  8  per  cent,  pure  potassium  cyanide,  and  boil  the  whole  in 
a  closed  iron  vessel  for  30  minutes.     The  proper  proportions 
for  the  solutions  are  as  follows :   First  alum  solution  :  Ammon- 
ium-alum 4  Ibs.,  warm  water   10  quarts.     Pearl-ash    solution  : 
Pearl-ash  4  Ibs.,  warm  water  10  quarts,  ammonium  carbonate 
4^2  to  5J^  drachms.     Second  alum  solution  :  Ammonium-alum 
8  Ibs.,  warm  water  25   quarts,  potassium  cyanide  4  Ibs.,  then 
add  20  quarts  of  water  and   about  4  Ibs.,   more   of  potassium 
cyanide,  and   let  the    whole    boil    for    about    J^    hour.      The 
filtered    solution    is    then    ready    for    use    as   the    electrolytic 
bath.     As  anodes  perforated  aluminium  plates  are  used,  which 
can  be  raised  and  lowered.     The  cathodes  receive  the  deposit. 
The  bath  is  maintained  at  a  temperature  of  between  80°  and 
149°  F.     By  adding  pieces  of  other  metals,  such  as  gold,  silver, 
nickel,  copper,  etc.,  to  the  aluminium  anodes,  the  color  of  the 
deposit  may  be  somewhat  changed.     If  the  deposit  shows  a 
gray  coloration  it  is  made  lustrous  by  dipping  in  a  solution  of 
caustic  soda,  which  also  prevents  oxidation. 

*  Neueste  Erfindungen  und  Erfahrungen,  vol.  xix.,  p.  353. 


350  ELECTRO-DEPOSITION    OF   METALS. 

Several  companies,  in  the  past,  have  been  selling  sheet  iron 
purporting  to  be  plated,  or  "  galvanized  "  as  they  call  it,  with 
aluminium  or  with  alloys  of  aluminium  and  tin.  It  is  a  fact 
that  alloys  of  aluminium  and  tin  can  be  coated  on  sheet  iron 
according  to  the  process  outlined  as  having  been  carried  on  by 
the  Tacony  Iron  &  Metal  Company  of  Philadelphia,  for  plating 
the  iron  columns  of  the  Public  Buildings  of  that  City,  but  in 
most  cases  sheet  iron  purporting  to  be  plated  with  alumin- 
ium have  been  found  on  analysis  to  contain  no  aluminium  at  all. 
In  the  plating  of  the  columns  of  the  Philadelphia  Public  Buildings 
by  the  Tacony  Iron  &  Metal  Company,  the  process  consisted  of 
plating  the  metal  with  an  alloy  of  75  per  cent,  aluminium  and  25 
per  cent.  tin.  The  iron  columns  were  first  cleansed  and  then 
electro- plated  with  copper  in  an  alkaline  bath,  a  thickness  of 
something  like  TV  inch  of  copper  being  obtained  in  an  acid 
sulphate  bath.  The  aluminium-tin  alloy  was  deposited  at  a 
temperature  of  130°  F.,  at  a  current  density  of  8  amperes  per 
square  foot,  from  pure  aluminium -anodes,  in  a  bath  having  the 
following  composition :  Saturated  solution  aluminate  of  soda 
75  parts,  stannate  of  soda  25  parts.  The  bath  also  contained 
some  potassium  cyanide. 

Electro-depositions  upon  aluminium. — The  electro-deposition 
of  other  metals  upon  aluminium  presents  many  difficulties 
which  are  chiefly  due  to  the  behavior  of  this  metal  in  the  plat- 
ing baths.  The  deposits  to  be  sure  are  formed  but  they 
possess  no  adherence,  and  especially  baths  containing  potas- 
sium cyanide  yield  the  worst  results  in  consequence  of  the 
effect  of  alkaline  solutions  upon  the  basis-metal.  Since  the 
production  of  aluminium  has  so  largely  increased  and  a  great 
number  of  articles  of  luxury  and  for  practical  use  are  now  made 
of  this  metal,  the  need  of  decorating  such  articles  by  electro- 
plating or  covering  them  entirely  with  other  metals  has  been 
felt,  since  the  color  of  aluminium  is  by  no  means  a  sympathetic 
one.  Look  into  a  show  window  where  aluminium  articles  are 
exposed — nothing  but  gray  in  gray.  Offended,  the  eye  of  the 
observer  turns  away  and  seeks  a  more  agreeable  rest. 


DEPOSITION    OF   ANTIMONY,  ARSENIC,  ALUMINIUM.         351 

Aluminium  behaves  so  differently  from  other  metals  towards 
the  cleansing  agents  usually  used  that  different  methods  from 
those  previously  described  have  to  be  employed  in  preparing 
it  for  plating.  Nitric  acid  has  almost  no  effect  on  aluminium, 
and  pickle  just  as  little ;  but,  on  the  other  hand,  the  metal  is 
attacked  by  concentrated  hydrochloric  acid,  dilute  hydrofluoric 
acid,  and  especially  by  alkaline  lyes.  Hence  if  polished  articles 
of  aluminium  are  to  be  prepared  for  plating,  alkaline  lyes  will 
have  to  be  avoided  in  freeing  them  from  grease,  it  being  best 
to  use  only  benzine  for  the  purpose.  Unpolished  articles  may 
without  hesitation  be  freed  from  grease  with  caustic  potash  or 
soda  lye,  and  for  the  production  of  a  dead  white  surface  be  for 
a  short  time  pickled  in  dilute  hydrofluoric  acid  and  then  thor- 
oughly rinsed  in  running  water.  For  producing  an  electro- 
deposit  upon  aluminium  it  has  been  considered  advisable  to 
first  copper  the  metal,  and  the  Aluminium  Gesellschaft  of 
Neuhausen  recommends  for  this  purpose  a  solution  of  nitrate  of 
copper.  But  the  adherence  of  the  copper  deposit  proved  also 
insufficient,  because  in  the  subsequent  silvering,  nickeling,  etc., 
the  deposit  raised  up. 

The  copper  bath  recommended  by  Delval,  consisting  of 
sodium  pyrophosphate  3  ozs.,  copper  sulphate  (copper 
vitriol)  y±  oz.,  sodium  bisulphite  ^  oz.,  water  I  quart,  also 
proved  unreliable. 

According  to  a  patented  process,  plating  of  aluminium  is 
claimed  to  be  effected  successfully  and  without  defect  by  lightly 
coating  the  metal  with  silver  amalgam  in  a  silver  bath  com- 
pounded with  potassium  mercury  cyanide.  However,  this 
treatment  also  did  not  always  yield  reliable  results. 

The  best  and  most  reliable  process  is  without  doubt  the  one 
patented,  in  1893,  by  Prof.  Nees.  It  consists  in  first  immersing 
the  aluminium  articles  previously  freed  from  grease  in  caustic 
soda  lye  until  the  action  of  the  lye  upon  the  metal  is  recognized 
by  gas  bubbles  rising  to  the  surface.  The  articles  without  be- 
ing previously  rinsed  are  then  for  a  few  minutes  immersed  in  a 
solution  of  77  troy  grains  of  chloride  of  mercury,  rinsed,  again 


352  ELECTRO-DEPOSITION   OF   METALS. 

brought  into  the  caustic  soda  lye  and  then,  without  rinsing, 
suspended  in  the  silver  bath.  The  deposit  of  silver  thus  ob- 
tained adheres  very  firmly,  and  can  be  scratch-brushed  and 
polished  with  the  steel  without  raising  up.  It  can  also  be 
directly  gilded,  brassed,  or,  after  previous  coppering  in  the 
potassium  cyanide  copper  bath,  provided  with  a  heavy  deposit 
of  nickel  and  polished  upon  polishing  disks. 

The  Mannesmann  Pipe  Works,  Germany,  produce  durable 
electro-deposits  by  brushing  the  aluminium  with  solutions  of 
sulphide  of  gold  and  sulphide  of  silver  in  balsam  of  sulphur* 
and  volatile  oils,  and  burning  in  the  metals  in  a  muffle  under 
exclusion  of  the  air  at  840°  to  930°  F.  The  thin  layers  of  metal 
which  are  separated  adhere  firmly  to  the  aluminium  and  are 
then  provided  with  any  electro-deposit  desired.  According  to 
a  process  patented  by  the  same  corporation  the  articles  are 
provided  with  a  firmly  adhering  (?)  film  of  zinc  by  immersing 
them  in  a  boiling  solution  of  zinc  dust  in  caustic  soda,  and  are 
then  electro-plated. 


CHAPTER  XIV. 

GALVANOPLASTY  (  REPRODUCTION) . 

BY  galvanoplasty  proper  is  understood  the  production,  with 
the  assistance  of  the  electric  current,  of  copies  of  articles  of 
various  kinds,  true  to  nature,  and  of  sufficient  thickness  to  form 
a  resisting  body,  which  may  be  separated  from  the  object 
serving  as  a  mould. 

Copper  is  the  most  suitable  metal  for  galvanoplastic  pro- 
cesses, that  which  is  precipitated  by  electrolysis  showing  the 
following  valuable  properties :  It  may  be  precipitated  chemic- 
ally pure,  and  in  this  state  is  less  capable  of  change  than  ordi- 

*  Solution  of  sulphur  in  linseed  oil. 


GALVANOPLASTY  (REPRODUCTION).          353 

nary  commercial  copper  or  the  ordinarily  used  copper  alloys,  its 
strength  of  extension  being  20  per  cent,  greater  than  that  of 
melted  copper ;  its  hardness  is  also  greater  than  that  of  melted 
copper,  while  its  specific  gravity  (8.85)  lies  between  that  of 
cast  and  rolled  copper. 

The  physical  properties  of  copper  deposited  by  electrolysis 
are  dependent  on  the  condition  of  the  bath,  as  well  as  on  the 
intensity  and  tension  of  the  working  current.  The  bath  used 
for  precipitating  the  copper  is  in  all  cases  a  solution  of  blue 
vitriol.  Smee  had  originally  proved  by  experiments  that  copper 
is  obtained  as  a  more  tenacious  and  fine-grained  deposit  when 
the  current-strength  is  as  great  as  possible,  without,  however, 
evolution  of  hydrogen  taking  place ;  while  copper  in  pulveru- 
lent, sandy  form  is  obtained  with  a  current-strength  that  liber- 
ates hydrogen,  and  in  coarsely  crystalline  form  when  the  cur- 
rent-strength is  very  slight. 

At  a  more  recent  period,  von  Hubl  instituted  a  series  of 
systematic  experiments  for  the  determination  of  the  conditions 
under  which  deposits  with  different  physical  properties  are  ob- 
tained. Hubl  worked  with  5  per  cent,  neutral,  and  5  per  cent, 
acid,  solutions  of  copper,  as  well  as  with  20  per  cent,  neutral, 
and  20  per  cent,  acid  solutions.  The  neutral  solutions  were 
prepared  by  boiling  blue  vitriol  solution  with  carbonate  of 
copper  in  excess,  and  the  acid  solutions  by  adding  2  percent, 
of  sulphuric  acid  of  66°  Be.  The  result  was  that  in  the  neutral 
5  per  cent,  solutions  less  brittle  deposits  were  obtained  with  a 
small  current-density  than  in  a  more  concentrated  solution, 
though  the  appearance  of  the  deposits  was  the  same.  The  ex- 
periments with  acidulated 'baths  confirmed  the  fact  that  free  sul- 
phuric .acid  promotes  the  formation  of  very  fine-grained  deposits 
even  with  very  slight^  current-densities,  and  it  appears  that  the 
brittleness  of  copper  deposited  from  acid  baths  is  influenced 
less  by  the  concentration  than  by  the  current-density  used. 

The  processes  used  in  galvanoplasty  may  be  arranged  in  two 
classes,  viz.,  the  deposition  of  copper  with  or  without  the  use  of 
external  sources  of  current,  the  first  comprising  galvanoplastic 
23 


354 


ELECTRO-DEPOSITION    OF   METALS. 


deposits  produced  by  means  of  the  single-cell  apparatus,  and 
the  other  those  by  the  battery  or  dynamo-machine. 

I.   Galvanoplastic  Deposition  in  the  Cell  Apparatus. 

The  cell  apparatus  consists  of  a  vessel  containing  blue  vitriol 
solution  kept  saturated  by  a  few  crystals  of  blue  vitriol  placed 
in  a  muslin  bag  or  a  small  perforated  box  of  wood,  stoneware, 
etc.  In  this  vessel  are  placed  round  or  square  porous  clay 
cells  (diaphragms)  which  contain  dilute  sulphuric  acid  and  a 
zinc  plate,  the  zinc  plates  being  connected  with  each  other  and 
with  the  objects  to  be  moulded — which  may  be  either  metallic 
or  made  conductive  by  graphite — by  copper  wire  or  copper 
rods.  The  objects  to  be  moulded  play  the  same  role  as  the 
copper  electrode  in  a  Daniell  element,  and  the  cell  apparatus 

FIG.  125. 


is  nothing  else  but  a  species  of  Daniell  element  in  which  the 
internal,  instead  of  an  external,  current  is  utilized.  As  soon  as 
the  circuit  is  closed  by  the  contact  of  the  objects  to  be  moulded 
with  the  zinc  of  the  porous  cell,  the  electrolytic  process  begins ; 
the  zinc  is  oxidized  by  the  oxygen  and  with  the  sulphuric  acid 
forms  zinc  sulphate  (white  vitriol),  while  the  copper  is  reduced 


GALVANOPLASTY  (REPRODUCTION). 


355 


from  the  blue  vitriol  solution  and  deposited  in  a  homogeneous 
layer  upon  the  articles  to  be  moulded. 

A  simple  apparatus,  frequently  used  by  amateurs  for  mould- 
ing metals,  reliefs,  etc.,  is  shown  in  Fig.  125. 

In  a  cylindrical  vessel  of  glass  or  stoneware  filled  with  satu- 
rated blue  vitriol  solution  is  placed  a  porous  clay  cell,  and  in 
the  latter  a  zinc  cylinder  projecting  about  0.039  to  0.079  inch 
above  the  porous  clay  cell.  To  the  zinc  is  soldered  a  copper 
ring,  as  plainly  shown  in  the  illustration.  The  clay  cell  is 
filled  with  dilute  sulphuric  acid  (i  acid  to  30  water),  to  which 
some  amalgamating  salt  may  be  suitably  added.  The  articles 
to  be  moulded  are  suspended  to  the  copper  ring,  care  being 
had  to  have  the  surfaces  which  are  to  be  covered  near  and 
opposite  to  the  cell.  To  supplement  the  content  of  copper, 
small  linen  or  sail-cloth  bags  filled  with  blue  vitriol  are  attached 
to  the  upper  edge  of  the  vessel. 

Fig.  126  shows  another  form  of  cell-apparatus  which  is 
much  used  in  printing  establishments  for  the  production  of 

FIG.  126. 


cliches.  A  is  a  large  box  lined  with  gutta-percha.  In  this 
box  is  suspended  a  smaller  box,  B,  the  bottom  of  which  is 
formed  of  a  disk  of  leather  or  parchment.  To  the  side  of  this 
box  are  nailed  strips,  b.  To  these  strips  is  secured  a  piece  of 
stout  linen,  which  serves  partially  as  a  support  of  the  zinc 
plate  Z  n  and  partially  to  prevent  impurities  of  the  zinc  from 


ELECTRO-DEPOSITION    OF   METALS. 

falling  upon  the  leather  disk.  The  zinc  plate  is  connected 
with  the  strap  K,  which  is  made  of  sheet  copper.  In  the  box 
A  lies  the  board  />,  which  is  sufficiently  weighted  with  strips 
of  lead  to  prevent  it  from  floating  in  the  fluid.  To  prevent  the 
separation  of  copper,  these  lead  strips  are  coated  with  a  varnish 
made  from  sealing-wax  or  with  gutta-percha.  To  the  upper 
side  of  the  board  is  nailed  the  copper  strap  K' ,  which  is  insu- 
lated as  far  as  it  touches  the  fluid  and  the  board  by  a  coating 
of  gutta-percha.  The  binding  screw  E  connects  the  two 
copper  straps.  A  perforated  copper  sheet  bent  in  the  form  of 
a  gutter  dips  above  in  the  copper  solution.  During  the  ope- 
ration this  copper  sheet  is  kept  filled  with  crystals  of  blue 
vitriol,  and  serves  to  maintain  a  uniform  saturation  of  the  fluid. 

To  produce  deposits  with  this  apparatus,  the  first  matrice  is 
laid  upon  the  portion  of  copper  strap  upon  the  board  D.  The 
copper  strap  is  then  connected  with  the  conducting  surface  by 
driving  a  brass  pin  through  the  matrice  and  the  strap  into  the 
board.  Underneath  the  other  end  of  the  matrice  is  placed  a 
small  piece  of  copper  sheet  insulated  by  gutta-percha,  so  that 
it  projects  y2  to  ^  inch  beneath  the  matrice.'  It  is  also 
brought  in  contact  with  the  conducting  surface  by  means  of  a 
brass  pin.  Upon  this  sheet  is  placed  the  second  matrice, 
which  is  also  secured  with  a  brass  pin,  and  so  on,  until  all  the 
moulds  upon  which  copper  is  to  be  precipitated  are  upon  the 
board.  The  surfaces  of  the  moulds,  as  well  as  the  heads  of 
the  pins,  are  then  carefully  rubbed  with  graphite,  and  the 
board  is  brought  into  the  box  filled  with  blue  vitriol  solution. 
The  box  B  with  the  zinc  plate  is  then  suspended  in  the  box  A, 
and  after  filling  it  with  dilute  sulphuric  acid,  the  two  copper 
straps  are  connected  by  the  binding  screw  E.  The  electric 
current  then  passes  through  the  latter  and  the  pin  to  the  sur- 
face of  the  first  matrice,  and  after  depositing  copper  upon  it 
passes  through  the  second  pin  and  the  small  copper  plate  to 
the  second  matrice,  and  so  on,  effecting  a  uniform  deposit  of 
copper  upon  all  conducting  surfaces  connected  with  each  other. 

Large  apparatus. — To  cover  large  surfaces,  use  large,  square 


GALVANOPLASTY  (REPRODUCTION). 


357 


vats  of  stoneware,  or  of  wood,  lined  with  lead,  gutta-percha,  or 
another  substance  unacted  upon  by  the  bath.  For  baths  up  to 
three  feet  long,  stoneware  vats  are  to  be  preferred. 

Fig.  127  shows  the  French  form  of  cell  apparatus.  In  the 
middle  of  the  vat,  and  in  the  direction  of  its  length,  is  disposed 
a  row  of  cylindrical  cells,  close  to  each  other,  each  provided 
with  its  zinc  cylinder.  A  thin  metallic  ribbon  is  connected 
with  all  the  binding  screws  of  the  cylinder,  and  is  in  contact  at 

FIG.  127. 


its  extremities  with  two  metallic  bands  on  the  ledges  of  the 
depositing  vat.  The  metallic  rods  supporting  the  moulds  are 
in  contact  with  the  metallic  bands  of  the  ledges,  and,  there- 
fore, in  connection  with  the  zincs. 

The  German  form  of  cell  apparattis  is  shown  in  Fig.  128.  It 
is  provided  with  long,  narrow,  rectangular  cells  of  a  correspond- 
ingly greater  height  than  the  column  of  fluid. 

Across  the  vat  are  placed  three  conducting  rods  connected 
with  each  other  by  binding  screws  and  copper  wire.  To  the 
centre  rod,  which  lies  over  the  cells,  are  suspended  the  zinc 


358 


ELECTRO-DEPOSITION   OF    METALS. 


plates  by  means  of  a  hook,  while  the  two  outer  rods  serve  for 
the  reception  of  the  moulds. 


FIG.  128. 


The  size  of  the  zinc  surfaces  in  the  simple  apparatus  should 
be  about  equal  to  that  of  the  surfaces  to  be  moulded,  if  dilute  sul- 
phuric acid  (i  acid  to  30  water)  is  to  be  used.  For  particulars 
see  "  Execution  of  the  Galvanoplastic  Deposition  of  Copper." 

The  copper  bath  for  the  cell  apparatus  consists  best  of  a  mode- 
rately saturated  solution  of  pure  blue  vitrol,  free  from  iron,  in 
water  free  from  lime,  and  should  show  about  18°  to  20°  Be.,  a 
bath  of  100  quarts  requiring  about  20  to  24  Ibs.  of  blue  vitriol. 
The  following  table  gives  the  approximate  content  of  pure 
crystallized  blue  vitriol  at  different  degrees  Be.,  and  at  59°  F. 


Degrees,  Be. 

Weight  by  volume. 

This  solution  contains 
crystallized  blue  vitriol. 

c°  . 

3 
] 

•035 

.072 
.088 
."3 

.121 
.130 

.138 
.147 

•»57 

.166 
.I76 

5  per  cent. 
ii 

13       " 
17       " 
18       " 
19 

20 
21 

23 

24 

25 

10° 

12°    

I  cO    

16°   .. 

17°    • 

18°  :::::::::::::::.:::  

IQo    .                                                

2QO    

21°    

22°    

GALVANOPLASTY  (REPRODUCTION).          359 

While  to  a  copper  bath  working  with  the  use  of  an  external 
source  of  current,  more  or  less  sulphuric  acid  is  added,  accord- 
ing to  requirement,  baths  in  the  single  cell  apparatus  do  not 
require  such  addition,  because  a  considerable  quantity  of  the 
acid  in  the  clay  cell  gradually  penetrates  by  osmose  into  the 
bath,  and  not  only  of  the  acid  alone,  but  also  of  the  white 
vitriol  solution  formed,  whereby  the  working  duration  of  the 
bath  is  considerably  reduced.  Furthermore,  the  sulphuric 
acid  liberated  by  the  separation  of  copper  from  the  blue  vitriol 
finds  no  saturation ;  so  that  such  a  bath  finally  contains  an  ex- 
cess of  acid  which  for  the  production  of  good  deposits  must 
from  time  to  time  be  removed,  if  it  is  not  preferred  to  throw 
the  bath  away  and  make  a  fresh  one.  The  simplest  method  of 
removing  the  excess  of  acid  is  to  add  to  the  bath  pure  carbon- 
ate of  copper  as  long  as  strong  effervescence  takes  place,  blue 
vitriol  being  thereby  formed,  and  hence  the  bath  at  the  same 
time  strengthened.  Some  operators  remove  the  excess  of 
acid  by  adding  to  the  bath  whiting  free  from  iron  until  no 
more  effervescence  takes  place,  and  then  filtering  off  from  the 
calcium  sulphate  (gypsum)  formed.  The  first-mentioned  pro- 
cess is,  however,  preferable  in  every  respect. 

2.   Galvanoplastic  Deposition  by  the  Battery  and  Dynamo- 
Machine. 

Since  it  has  been  shown  in  the  preceding  section  that  a  cell 
apparatus  is  to  be  considered  as  a  Daniell  element  closed  in 
itself,  it  will  not  be  difficult  to  comprehend  that  in  economical 
respects  no  advantage  is  offered  by  the  production  of  galvano- 
plastic  depositions  by  a  separate  battery,  because  in  both  cases 
the  chemical  work  is  the  same  and  the  zinc  dissolved  by  the 
use  of  the  Daniell  or  Bunsen  element  effects  no  greater  quantity 
of  copper  deposit  in  the  bath  than  the  same  quantity  of  zinc 
dissolved  in  the  cells  of  the  single  apparatus.  In  other  re- 
spects the  use  of  a  battery,  however,  offers  great  advantages. 
The  employment  of  external  sources  of  current  requires  the 
same  arrangement  as  shown  in  Figs.  52  and  54,  pp.  96  and  98  ; 


360  ELECTRO- DEPOSITION    OF   METALS. 

copper  anodes  being  placed   in  the  bath,  which  are  connected 
with  the  anode  pole  of  the  battery. 

By  this  arrangement,  while  the  copper  is  being  deposited 
upon  the  mould,  the  copper  anodes  become  dissolved  by  the 
sulphuric  acid  set  free,  forming  sulphate  of  copper,  which  con- 
tinued action  keeps  the  copper  content  of  the  bath  quite  con- 
stant. Furthermore,  no  foreign  metallic  admixtures  reach  the 
bath,  as  is  the  case  in  the  single  cell  apparatus,  by  the  white 
vitriol  solution  penetrating  from  the  clay  cell  into  the  bath  and 
causing  the  formation  of  rough  and  brittle  deposits  of  copper. 
The  principal  advantage,  however,  is  that  by  placing  a  resist- 
ance board  in  the  circuit  the  current-strength  can  be  controlled 
so  that  the  deposits  can  be  quickly  covered  with  a  strong 
current  and  then  augmented  with  a  weaker  current,  and  that 
by  intelligently  regulating  the  current-strength,  deep  depres- 
sions can  also  be  covered,  which  is  difficult  in  the  single  cell 
apparatus. 

A.  Depositions  with  the  Battery. 

The  Daniell  element  described  on  p.  35,  which  yields  a 
tension  of  about  I  volt,  is  much  liked  for  this  purpose.  Since 
the  copper  bath  for  galvanoplastic  purposes  requires  for  its  de- 
composition an  electromotive  force  of  only  0.5  to  I  volts,  it  will 
be  best  for  slightly  depressed  moulds  to  couple  the  elements 
for  quantity  (Fig.  3,  p.  20),  alongside  of  each  other;  and  only 
in  cases  where  the  particular  kind  of  moulds  requires  a  current 
of  stronger  tension,  to  couple  two  elements  for  tension  one 
after  the  other,  an  excess  of  current  being  rendered  innoxious 
by  means  of  the  resistance  board  or  by  suspending  larger 
surfaces. 

Bunsen  elements  may,  however,  be  used  to  great  advantage, 
since  the  zincs  of  the  Daniell  elements  become  tarnished  with 
copper  and  have  to  be  frequently  cleansed  if  the  process  is  not 
to  be  retarded  or  entirely  interrupted.  The  Bunsen  elements 
need  only  be  coupled  for  quantity,  their  electromotive  power 
being  considerably  greater.  To  be  sure,  the  running  expenses 


GALVANOPLASTY  (REPRODUCTION).          361 

are  much  greater  than  with  Daniell  elements,  at  least  when 
nitric  acid  is  used  for  filling.  All  that  has  been  said  under 
"  Electro-plating  arrangements  in  particular,"  p.  89,  in  regard 
to  conducting  the  current,  the  resistance  boards,  conducting 
rod,  anodes,  etc.,  is  also  valid  for  plants  for  the  galvanoplastic 
deposition  of  copper  with  the  battery. 

B.  Depositions  with  Dynamo- Machines. 

It  is  best  to  use  dynamos  capable  of  yielding  a  large  quantity 
of  current  with  a  tension  of  2,  or,  at  the  utmost,  2^/2  volts.  In 
order  to  avoid  repetition,  the  reader  is  referred  to  what  has 
been  said  under  "  Arrangements  with  dynamo-electric  ma- 
chines," p.  109,  the  directions  given  there  applying  also  to  the 
galvanoplastic  process.  Since  only  in  very  rare  cases  the 
object-surface  will  be  the  same  in  all  baths,  it  will  be  advisable 
to  supply  each  of  the  baths,  if  several  of  them  are  worked  with 
one  dynamo-machine,  with  a  resistance-board  and  a  voltmeter. 

Copper  baths  for  galvanoplastic  depositions  with  a  separate 
source  of  current. — The  directions  for  the  composition  of  the 
bath  vary  very  much,  some  authors  recommending  a  copper 
solution  of  1 8°  Be.  which  is  brought  up  to  22°  Be.  by  the  addi- 
tion of  pure  concentrated  sulphuric  acid.  Others  again  increase 
the  specific  gravity  of  the  bath  up  to  25°  Be.  by  the  addition  of 
sulphuric  acid,  while  some  prescribe  an  addition  of  5  to  7  per 
cent,  of  sulphuric  acid.  It  is  difficult  to  give  a  general  formula 
suitable  for  all  cases,  because  the  addition  of  sulphuric  acid  will 
vary  according  to  the  current-strength  at  disposal,  the  nature  of 
the  moulds,  and  the  distance  of  the  anodes  from  the  objects. 
The  object  of  adding  sulphuric  acid  is,  on  the  one  hand,  to 
render  the  bath  more  conductive  and,  when  used  in  proper  pro- 
portions, to  make  the  deposit  more  elastic  and  smoother,  and 
prevent  the  brittleness  and  coarse-grained  structure  which, 
under  certain  conditions,  appear.  When  depositing  with  a 
battery,  somewhat  more  sulphuric  acid  may  be  added  to  the 
bath  than  when  employing  the  current  of  a  dynamo-electric 
machine.  The  following  compositions  have,  in  most  cases, 


362  ELECTRO-DEPOSITION    OF   METALS. 

been  found  suitable  for  the  reproduction  of  shallow  as  well  as 
of  deep  moulds. 

I.  For  depositing  with  the  dynamo. — Blue  vitriol  solution  of 
1 8°   Be.    100  quarts,  pure  sulphuric  acid  of  66°   Be.   I  to  I  y2 
quarts. 

II.  For  depositing  with  the  battery. — Blue  vitriol  solution   of 
18°  Be.  100  quarts,  pure  sulphuric  acid  of  66°   Be.  I  ^   to  2 
quarts. 

For  some  special  uses,  the  composition  of  the  bath  has  to  be 
somewhat  modified,  which  will  be  referred  to  later  on.  In  re- 
gard to  the  elasticity,  strength  and  hardness  of  galvanoplastic 
depositions  of  copper,  v.  Hubl  found  that  copper  of  great 
toughness,  but  of  less  hardness  and  strength,  is  obtained  with  a 
current  density  of  0.6-1.0  ampere  from  an  18  per  cent,  blue 
vitriol  solution,  and  copper  of  great  hardness  and  strength,  but 
of  little  toughness,  with  2  to  3  amperes,  from  a  20  per  cent, 
solution. 

For  copper  printing-plates,  a  20  per  cent,  solution,  com- 
pounded with  3  per  cent,  of  sulphuric  acid,  and  with  the  use  of 
a  current-density  of  1.3  amperes,  was  found  most  suitable. 

Many  operators  prefer  as  a  bath  a  solution  of  pure  blue  vitriol 
of  22°  Be.,  without  any  addition  of  sulphuric  acid.  A  good 
deposit  is  obtained  in  such  a  bath,  but  a  tension  of  2  to  2^ 
volts  is  required,  while  acidulated  baths  need  only  ^  to  I J^ 
volts,  according  to  the  content  of  acid. 

Very  fine  deposits  have  also  been  obtained  in  baths  consist- 
ing of  a  blue  vitriol  solution  of  21°  Be,  brought  up  to  22°  by 
the  addition  of  sulphuric  acid.  This  shows  that  it  is  not  neces- 
sary to  stick  to  a  fixed  unlimited  composition  of  the  baths, 
provided  it  is  understood  how  to  bring  the  current-condition 
into  harmony  with  the  composition. 

According  to  the  composition  of  the  bath,  a  fixed  minimum 
and  maximum  current-density  correspond  to  it,  which  must 
not  be  exceeded  if  useful  deposits  are  to  be  obtained.  There 
is,  however,  a  further  difference  according  to  whether  the 
bath  is  at  rest  or  in  motion,  v.  Hubl  obtained  the  following 
results : — 


GALVANOPLASTY  (REPRODUCTION). 


363 


Composition  of  solution. 

Minimum  and  maximum  current-density 
per  15.5  square  inches. 

With  solution  at 
rest. 
Amperes. 

With  solution  in 
gentle  motion. 
Amperes. 

15  per  cent,  blue  vitriol,  without  sulphuric 

2.6  to  3.9 

1-5    "    2'3 

3-4  "  5-i 

2.0   "   3.0 

3.9  to  5.2 
2.3  «  3.0 
5.1  «  6.8 
3.0  "  4.0 

15  per  cent,  blue  vitriol, 
sulphuric  3-cid 

with  6  per  cent. 

20  per  cent,  blue  vitriol,  without  sulphuric 

20  per  cent,  blue  vitriol, 

with  6  per  cent. 

Touching  the  addition  of  sulphuric  acid,  it  was  shown  that 
no  difference  in  the  texture  of  the  deposit  is  perceptible  if  the 
addition  of  acid  varies  between  2  and  8  per  cent. 

The  preceding  table  shows  that  a  copper  bath  in  gentle 
motion  can  stand  considerably  higher  current  densities,  and 
hence  will  work  with  correspondingly  greater  activity  than  a 
bath  at  rest.  In  the  electrolytic  refining  of  copper  it  was 
found  that  for  the  faultless  deposition  of  copper  the  bath  must 
be  maintained  entirely  homogeneous  in  all  its  parts.  When  a 
copper  bath  is  at  rest  and  the  depositing  operation  in  progress, 
the  upper  layers  of  the  bath  become  poorer  in  copper  than 
the  lower,  while  at  the  same  time  they  contain  more  sulphuric 
acid.  This  difference  in  the  composition  of  the  upper  and 
lower  layers  has  the  disadvantage  that  the  portions  dipping 
into  the  layers  richer  in  copper  become  more  thickly  coppered 
than  those  in  the  upper  layers.  Baths  which  are  constantly 
in  gentle  motion  show  less  inclination  to  the  formation  of 
knots  and  other  rough  excrescences,  and  hence  the  current- 
density  may  be  greater  than  with  solutions  at  rest  resulting  in 
the  deposition  being  effected  with  greater  rapidity.  These 
experiences  gathered  in  electro-metallurgical  operations  on  a 
large  scale,  have  been  advantageously  applied  to  galvanoplasty. 
The  constant  motion  of  the  copper  bath  may  be  effected  in 


ELECTRO-DEPOSITION    OF    METALS. 


various  ways.  Stirring  by  hand 
is  frequently  relied  upon,  but  it 
is  liable  to  be  accidentally 
omitted,  and  being  of  necessity 
intermittent  allows  time  for 
partial  separation  to  occur  be- 
tween two  consecutive  stirrings. 
Mechanical  agitation,  which  is 
more  certain  in  its  effects,  may 
be  applied  by  working  a  small 
screw  propeller  slowly  at  one 
end  of  the  bath,  or  by  blowing 
air  into  the  solution  constantly 
through  a  tube  passing  to  the 
bottom  of  the  vat,  by  means  of 
a  fan-blower  or  other  arrange- 
ment. 

Where  many  copper  baths 
are  in  operation,  the  agitation 
of  the  bath  may  be  effected  as 
follows  :  The  baths  are  arranged 
in  the  form  of  steps ;  near  the 
bottom  each  bath  is  provided 
with  a  leaden  outlet-pipe  (Fig. 
129),  which  terminates  over 
the  next  bath  over  a  distribut- 
ing gutter,  or  as  a  perforated 
pipe,  //.  From  the  last  bath 
the  copper  solution  flows  into  a 
reservoir,  E,  from  which  it  is 
forced'  by  means  of  a  hard- 
rubber  pump,  z,  into  the  reser- 
voir, A,  placed  at  a  higher 
level ;  from  A  it  again  passes 
through  the  baths  B,  C,  and 
D.  A  leaden  steam  coil  may, 


GALVANOPLASTY  (REPRODUCTION).          365 

if  necessary,  be  placed  in  A,  to  increase  the  temperature  if  it 
should  have  become  too  low.  Over  A  a  wooden  frame  cov- 
ered with  felt  may  be  placed ;  the  copper  solution  flowing 
upon  the  frame  and  passing  through  the  felt  is  thereby  filtered. 

Whatever  motion  is  given  to  the  bath  it  must  be  sufficiently 
vigorous  to  insure  thorough  mixture  of  the  solution,  but  with- 
out disturbing  the  relative  positions  of  anode  and  cathode,  and 
the  mechanism  must  be  so  applied  that  it  in  no  way  lessens  the 
facilities  for  examining  the  progress  of  deposition. 

Annealed  sheets  of  pure  copper  are  used  as  anodes ;  impure 
anodes  introduce  other  metallic  constituents  into  the  bath, 
which  might  result  in  a  brittle  deposit.  It  is  recommended 
daily  to  free  the  anodes  from  adhering  residues  by  brushing, 
so  as  to  decrease  the  collection  of  slime  in  the  bath. 

The  anodes  should '  present  at  least  as  large  a  surface  as  the 
cathodes ;  for  flat  moulds  the  distance  between  them  and  the 
anodes  may  be  two  to  three  inches,  but  has  to  be  increased  for 
deeper  .moulds.  The  copper  withdrawn  from  the  bath  by 
deposition  being  only  partially  replaced  by  the  anodes,  the  con- 
tent of  free  acid  will  increase  in  consequence  of  the  reduction 
of  the  content  of  copper.  •  However,  the  copper  wanting  can  be 
readily  replaced  by  suspending  bags  filled  with  blue  vitriol  in 
the  bath,  while  too  large  an  excess  of  acid  is  removed  by  the 
addition  of  copper  carbonate. 

Determination  of  free  acid.  The  free  acid  is  determined  by 
titrating  the  copper  solution  with  normal  soda  solution,  congo 
paper  being  used  as  an  indicator.  Bring  by  means  of  a  pipette, 
10  cubic  centimeters  of  the  copper  bath  into  a  beaker  glass, 
dilute  with  the  same  quantity  of  distilled  water,  and  add  drop 
by  drop  from  a  burette  normal  soda  solution,  stirring  con- 
stantly, until  congo  paper  is  no  longer  colored  blue,  when 
moistened  with  a  drop  of  the  solution  in  the  beaker  glass. 
The  cubic  centimeters  of  normal  soda  solution  consumed 
multiplied  by  4.9  gives  the  number  of  grammes  of  sulphuric 
acid  in  the  liter. 

Suppose  up  to  the  appearance  of  the  final  reaction  by  means 


366  ELECTRO-DEPOSITION    OF   METALS. 

of  congo  paper,  which  indicates  that  all  the  free  sulphuric  acid 
has  been  saturated  by  the  normal  soda  solution,  11.99  cubic 
centimeters  of  normal  soda  solution  had  been  used  for  TO 
cubic  centimeters  of  copper  bath,  then  one  liter  of  the  bath 
contains  11.9x4.9  =  58.31  grammes  of  sulphuric  acid. 

Determination  of  the  content  of  copper  according  to  Hacn. — 
This  method  is  based  upon  the  conversion  of  blue  vitriol  and 
potassium  iodide  into  copper  iodide  and  free  iodine.  By  de- 
termining the  quantity  of  separated  free  iodine  by  titrating 
with  solution  of  sodium  hyposulphite  of  known  content,  the 
content  of  blue  vitriol  is  found  by  simple  calculation.  The 
process  is  as  follows  :  Bring  10  cubic  centimetres  of  the  copper 
bath  into  a  measuring  flask  holding  T\  liter,  neutralize  the 
freed  acid  by  the  addition  of  dilute  soda  lye  until  a  precipitate 
of  bluish  cupric  hydrate,  which  does  not  disappear  even  with 
vigorous  shaking,  commences  to  separate.  Now  add,  drop  by 
drop,  dilute  sulphuric  acid  until  the  precipitate  just  dissolves ; 
then  fill  the  measuring  flask  up  to  the  mark  with  distilled 
water,  and  mix  by  vigorous  shaking.  Of  this  solution  bring 
10  cubic  centimetres  by  means  of  a  pipette  into  a  flask  of  100 
cubic  centimetres'  capacity  and  provided  with  a  glass  stopper; 
add  10  cubic  centimetres  of  a  10  per  cent,  potassium  iodide 
solution,  dilute  with  some  water,  and  allow  the  closed  vessel  to 
stand  about  10  minutes.  Now  add  from  a  burette,  with  con- 
stant stirring,  a  decinormal  solution  of  sodium  hyposulphite 
until  starch-paper  is  no  longer  colored  blue  by  a  drop  of  the 
solution  in  the  flask.  Since  I  cubic  centimetre  of  deci- 
normal solution  corresponds  to  0.0249  grammes  of  blue  vitriol 
(=0.0063  gramme  of  copper),  the  content  of  blue  vitriol  in 
one  liter  of  the  solution  is  found  by  multiplying  the  number  of 
cubic  centimetres  of  decinormal  solution  consumed  by  24.9. 
For  the  correctness  of  the  result  it  is  necessary  that  the  copper 
bath  should  be  free  from  iron. 

Suppose  7.2  cubic  centimetres  of  decinormal  solution  of  sod- 
ium hyposulphite  have  been  used,  the  bath  would  contain 
7.2  x  24-9  =  179.28  grammes  of  blue  vitriol. 


GALVANOPLASTY  (REPRODUCTION).          367 

If  now  by  these  two  determinations,  the  content  of  free  acid 
and  of  blue  vitriol  in  the  bath  has  been  ascertained,  a  com- 
parison with  the  contents  originally  present  in  preparing  the 
bath  will  show  how  many  grammes  per  liter  the  content  of  acid 
has  increased,  and  how  many  grammes  the  content  of  copper 
has  decreased.  Then  by  a  simple  calculation  it  is  found  how 
much  dry  pure  carbonate  of  copper  has  to  be  added  per  liter  of 
solution  to  restore  the  original  composition.  For  each  gramme 
more  of  sulphuric  acid  than  originally  present,  1.26  grammes  of 
carbonate  of  copper  have  to  be  added,  and  each  gramme  of 
carbonate  of  copper  increases  the  content  of  blue  vitriol  2.02 
grammes  per  liter  of  bath.  By  reference  to  these  data  the 
operator  is  enabled  to  calculate  whether  the  quantity  of  carbon- 
ate of  copper  added  for  the  neutralization  of  the  excess  of  free 
acid  suffices  to  restore  the  original  content  of  blue  vitriol; 
or  whether,  and  how  much,  blue  vitriol  per  liter  has  to  be 
added. 

Preparation  of  moulds  (matrices"}  in  plastic  material. — If  a 
negative  of  the  original  for  the  production  of  copies  is  not  to  be 
made  by  direct  deposition  upon  a  metallic  object,  the  negative 
has  to  be  prepared  by  moulding  the  original  in  a  plastic  mass, 
which  on  hardening  will  retain  the  forms  and  lines  of  the  design 
to  the  finest  hatchings.  Gutta-percha,  wax  (stearine,  etc.), 
plaster  of  Paris,  glue,  and  a  few  readily  fusible  metals  are  suit- 
able materials  for  this  purpose. 

Since  the  galvanoplastic  process  as  far  as  it  applies  to  electro- 
typing,  will  next  be  considered,  we  first  direct  our  attention  to 
the  preparation  of  moulds  or  matrices  of  gutta-percha  and  wax, 
the  only  materials  suitable  for  this  purpose,  and  which  are 
generally  used. 

I.  Moulding  in  gutta-percha. — For  the  reproduction  of  the 
fine  lines  of  a  wood-cut  or  copper-plate,  pure  gutta-percha  freed 
by  various  cleansing  processes  from  the  woody  fibres,  earthy 
substances,  etc.,  found  in  the  crude  product,  is  very  suitable. 
Besides  the  requisite  degree  of  purity,  the  gutta-percha  should 
possess  three  other  properties,  viz.,  it  must  become  highly 


ELECTRO-DEPOSITION    OF   METALS. 

plastic  by  heating,  without,  however,  becoming  sticky,  and 
finally  it  should  rapidly  harden. 

The  most  simple  way  of  softening  gutta-percha  is  to  place  it 
in  water  of  176°  to  194°  F.  When  thoroughly  softened  no 
hard  lumps  should  be  felt  in  kneading  with  the  hands,  in  doing 
which  the  latter  should  be  kept  thoroughly  moistened  with 
water.  A  fragment  corresponding  to  the  size  of  the  object  to 
be  moulded  is  then  rolled  into  a  plate  about  J^  to  ^  inch  thick. 
To  facilitate  the  detachment  of  the  mould  after  cooling,  the 
surfaces  of  the  objects  to  be  moulded,  as  well  as  the  side  of  the 
gutta-percha  which  is  to  receive  the  impression,  should  be  well 
brushed  with  black-lead  (plumbago  or  graphite).  The  black- 
leaded  surfaces  are  then  placed  one  upon  the  other,  and  after 
gently  pressing  the  gutta-percha  with  the  hand  upon  the 
original  the  whole  is  placed  in  the  press.  To  stop  the  further 
movement  of  the  press-plate  and  prevent  injury  to  the  mould 
by  too  strong  a  pressure,  small  iron  blocks,  somewhat  higher 
than  the  frame  containing  the  object  to  be  moulded  and  the 
gutta-percha  plates  are  placed  on  both  sides  of  the  frame.  The 
screw  of  the  press  is  then  made  to  act  until  the  press-plate 
touches  the  iron  blocks ;  under  this  pressure  the  gutta-percha 
is  allowed  to  cool  and  harden. 

For  making  the  impression  of  the  form  in  the  moulding  com- 
position, a  moulding  press  is  used  which  is  capable  of  giving  a 
gradual  and  powerful  pressure.  Fig.  130  represents  a  form  of 
moulding  press  in  common  use,  and  known  as  the  "toggle" 
press.  It  consists  of  a  massive  frame  having  a  planed  movable 
bed  over  which  a  head  is  swung  on  pivots  and  counter-balanced 
by  a  heavy-weight,  as  shown,  so  that  it  can  be  readily  thrown 
up,  leaving  the  bed  exposed,  the  black-leaded  type-form  being 
placed  on  the  bed.  The  well  black-leaded  case  is  attached  by 
clamps  to  the  movable  head,  or  the  form  (also  black-leaded)  is 
laid  face  down  on  the  case,  and  the  head  is  then  turned  down 
and  held  in  place  by  the  swinging  bar  (shown  turned  back  in 
the  cut).  All  being  ready,  the  toggle-pressure  is  put  on  by 
means  of  the  hand-wheel  and  screw,  the  result  being  to  raise 


GALVANOPLASTY  ( REPRODUCTION) . 


369 


the  bed  of  the  press  with  an  enormous  pressure,  causing  the 
face  of  the  type-form  to  impress  itself  into  the  exposed  mould- 
ing surface. 

FIG.  130. 


Fig.  131  represents  a  form  of  "  hydraulic  press"  less  com- 
monly used  than  that  just  described.  It  is  provided  with  pro- 
jecting rails  and  sliding  plate,  on  which  the  form  and  case  are 
arranged  before  being  placed  in  the  press.  The  pump,  which 
is  worked  by  hand,  is  supported  by  a  frame-work  on  the  cistern 
below  the  cylinder,  and  is  furnished  with  a  graduated  adjust- 
able safety-valve  to  give  any  desired  pressure. 
24 


ELECTRO-DEPOSITION    OF   METALS. 
FIG.  131. 


2.  Moulding  in  wax  (stearine). — Beeswax  is  a  very  useful 
material  for  preparing  moulds,  but,  like  stearine,  it  is  accord- 
ing to  the  temperature  now  softer  and  now  harder,  which  must 
be  taken  into  consideration.  In  the  cold,  pure  beeswax  is 
quite  brittle  and  apt  to  become  full  of  fissures  in  pressing.  To 
decrease  the  brittleness  certain  additions  are  made  to  the  wax, 
Urquart  recommending  the  following  mixture,  which  is  fre- 
quently used  in  England:  Beeswax  85  parts  by  weight,  Venice 
turpentine  13,  black-lead  finely  pulverized  2. 

According  to  Volkmer,  a  good  mixture  is  obtained  by  melt- 
ing together  70  parts  of  wax  and  30  of  stearine.  Watt  prefers 
a  mixture  consisting  of  70  parts  of  wax,  26  of  stearine,  and  4 
of  litharge  or  flake-white.  G.  L.  v.  Kress  recommends  the 
following  mixture:  White  wax  42.32  ozs.,  stearine  14.11  to 
21.16  ozs.,  tallow  10.58  ozs.,  graphite  1.76  ozs.  First  melt  the 
asphalt  over  a  moderate  fire,  then  add  the  wax,  stearine,  and 


GALVANOPLASTY  (REPRODUCTION). 


371 


tallow,  and  when  these  are  melted,  the  graphite ;   stir  until  the 
mixture  begins  to  congeal. 

To  prepare  the  wax  mould  pour  the  melted  composition 
into  flat  metallic  trays  provided  with  loops  for  suspension  in 
the  bath.  When  the  composition  is  nearly  set  remove  any 
bubbles  of  air  or  impurities  from  the  surface  with  blotting- 

FIG.  132. 


paper.  After  black-leading  the  surface  press  the  original,  also 
black-leaded,  upon  the  composition  and  submit  the  whole  to 
pressure  until  cold.  When  the  black-leading  has  been  care- 
fully done  there  is  no  difficulty  in  detaching  the  original  after 
cooling ;  many  operators  slightly  oil  the  surface  of  the  original 
instead  of  black-leading. 


3/2  ELECTRO-DEPOSITION    OF    METALS. 

When  the  mould  of  gutta-percha  or  wax  has  been  properly 
made,  it  is  thoroughly  black-leaded  in  order  to  give  it  a  con- 
ducting surface  upon  which  the  electro-deposition  of  the  copper 
may  take  place.  Black-leading  must  be  very  thorough  so  that 
the  black-lead  penetrates  into  every  line  and  letter  of  the  mould, 
otherwise  the  copper  deposited  on  the  surface  will  be  an  im- 
perfect copy  of  the  original,  and  it  will  be  useless  to  place  the 
mould  in  the  bath.  The  black-lead  used  in  every  stage  of  the 
electrotyping  process  must  be  of  the  purest  description  and  in 
the  most  minute  state  of  division.  The  best  material  for  the 
purpose  is  prepared  from  the  purest  selected  Ceylon  graphite, 
which  is  ground  by  rolling  with  heavy  iron  balls  until  it  is  re- 
duced to  a  dead-black,  impalpable  powder. 

Black-leading  the  moulds  is  performed  either  by  hand  or 
more  commonly  by  machines. 

Fig.  132  shows  one  of  these  machines  with  its  cover  removed 
to  exhibit  its  construction.  It  has  a  traveling  carriage  holding 
one  or  more  forms,  which  passes  backward  and  forward,  under 
a  laterally  vibrating  brush.  Beneath  the  machine  is  placed  an 
apron  which  catches  the  powder,  which  is  again  used. 

Another  construction  of  a  black-leading  machine  is  shown  in 
Fig.  133,  the  details  of  which  will  be  understood  without  lengthy 
description.  The  moulds  are  placed  upon  the  slowly  revolving, 
horizontal  wheel  upon  which  the  brush  moves  rapidly  up  and 
down  with  a  vertical,  and  at  the  same  time  laterally,  vibrating 
motion.  The  black-leading  space  being  closed  air-tight,  scat- 
tering of  black-lead  dust  is  entirely  prevented,  the  excess  of 
black-lead  collecting  in  a  vessel  placed  in  the  pedestal. 

On  account  of  the  dirt  and  dust  caused  by  the  dry  process 
of  black- leading,  some  electrotypers  prefer  the  wet  process  in- 
vented by  Mr.  Silas  P.  Knight,  of  New  York.  This  process  is 
designed  to  work  more  quickly  and  neatly,  producing  moulds 
that  are  thinly,  evenly,  and  perfectly  covered.  The  moulds  are 
placed  upon  a  shelf  in  a  suitable  receptacle,  and  a  rqtary  pump 
forces  an  emulsion  of  graphite  and  water  over  their  surfaces 
through  a  traveling  fine-rose  nozzle.  This  process  is  pro- 
nounced to  be  rapid,  efficient,  neat,  and  economical. 


GALVANOPLASTY  (REPRODUCTION). 


373 


With  very  deep  forms  of  type,  it  is  sometimes  of  advantage 
to  first  coat  the  black-leaded  surface  with  copper,  in  order  to 
obtain  a  uniform  deposit  in  the  bath.  The  process  is  as  fol- 
lows :  Pour  alcohol  over  the  black-leaded  form,  let  it  run  off 
and  then  place  the  form  horizontally  over  a  water  trough. 
Now  pour  over  the  form  blue  vitriol  solution  of  15°  to  1 6°  Be., 
dust  upon  it  from  a  pepper-box  some  impalpably  fine  iron  fil- 

FIG.  133. 


ings  and  brush  the  mixture  over  the  whole  surface,  which  thus 
becomes  coated  with  a  thin,  bright,  adherent  film  of  copper. 
Should  any  portion  of  the  surface  after  such  treatment  remain 
uncoppered,  the  operation  is  repeated.  The  excess  of  copper 
is  washed  off  and  the  form,  after  being  provided  with  the  neces- 
sary conducting  wires,  is  ready  for  the  bath. 

Gilt  or  silvered  black-lead  is  also  sometimes  used  for  very 
deep  forms.  It  is,  however,  cheaper  to  mix  the  black-lead 
with  y±  its  weight  of  finest  white  bronze  powder  from  finely 


374  ELECTRO-DEPOSITION   OF   METALS. 

divided  tin.  When  forms  thus  black-leaded  are  brought  into 
the  copper  bath,  the  particles  of  tin  become  coated  with 
copper,  also  causing  a  deposit  upon  the  black-lead  particles  in 
contact  with  them. 

After  black-leading  the  workman  takes  one  or  several  stout 
copper  wires,  the  ends  of  which,  after  thorough  cleansing,  he 
heats  for  an  instant,  and  imbeds  them  in  the  wax  on  the  side  of 
the  mould.  The  surface  of  this  wire  is  carefully  exposed,  and 
by  way  of  precaution  the  place  is  rubbed  with  black-lead  with 
the  finger  to  restore  the  black-lead  surface  that  may  have  been 
disturbed.  Trifling  as  this  circumstance  of  exposing  the  im- 
bedded wire  may  appear,  the  galvanic  deposit  of  the  copper 
on  the  face  of  the  mould  would  be  impossible  were  it  ne- 
glected, as  the  mass  of  wax  being  a  non-conductor  of  elec- 
tricity a  galvanic  current  could  not  otherwise  be  established. 
The  exposure  of  the  wire,  therefore,  is  essential  in  order  that 
the  surface  of  the  mould  may  be  rendered  properly  conductive 
to  insure  the  uniform  deposition  of  copper  upon  it.  To  con- 
fine the  deposit  of  copper  where  it  is  actually  desired,  and  to 
prevent  it  from  unnecessarily  spreading  over  the  edges  of  the 
mould,  a  tool  called  the  "  building  iron"  is  heated  and  run 
over  the  mould  so  as  to  destroy  the  continuity  of  the  black- 
lead  surface,  save  where  the  deposit  of  copper  is  wanted. 

In  order  that  the  deposition  of  copper  may  be  as  nearly  uni- 
form in  thickness  as  possible  over  the  entire  surface  of  the 
mould,  it  becomes  necessary,  where  a  large  surface  is  to  be 
coated,  to  provide  as  much  metallic  surface  as  possible  on 
which  the  deposit  of  copper  may  commence  and  spread.  One 
method  of  accomplishing  this,  is  to  attach  one  or  more  pieces 
of  metal  to  the  wax  on  the  edges  of  the  mould,  and  connect 
them  with  the  slinging  wires  by  good  metallic  connections. 

A  very  practical  device  in  this  connection  is  the  "  electric- 
connection  gripper  "  of  Messrs.  R.  Hoe  &  Co.,  of  New  York. 
This  arrangement  is  designed  to  hold  and  sustain  the  moulding 
case,  and  at  the  sane  time  to  make  an  electric  connection  with 
the  prepared  conducting  face  of  the  mould  only;  consequently, 


GALVANOPLASTY  (REPRODUCTION).          3/5 

leaving  the  metal  case  itself  entirely  out  of  the  current,  so  that 
no  copper  can  be  deposited  on  it. 

Gutta-percha  being  specifically  lighter  than  water,  moulds  of 
this  material  have  to  be  provided  with  a  piece  of  heated  lead 
stuck  to  the  back  to  prevent  them  from  floating,  and  to  force 
them  to  occupy  a  perpendicular  position  opposite  to  the  anodes. 

The  moulds  are  suspended  in  the  bath  in  the  same  manner 
as  in  other  galvanic  processes,  special  care  being  had  that  their 
surfaces  hang  parallel  to  the  anodes,  so  that  all  portions  may 
receive  a  uniform  deposit.  Before  placing  the  mould  in  the 
bath,  pour  over  it,  while  in  a  horizontal  position,  a  mixture  of 
equal  parts  of  alcohol  and  water ;  by  this  means,  a  uniform 
moistening  of  the  mould  in  the  bath  is  attained,  and  the  settle- 
ment of  air-bubbles  on  it  prevented. 

For  the  production  of  a  dense,  coherent,  and  elastic  deposit 
in  the  acid-copper  bath,  the  chief  requisite  is  to  have  the 
current-strength  in  the  correct  proportion  to  the  surface  to  be 
coated,  this  applying  to  deposition  with  the  single-cell  appar- 
atus, as  well  as  with  an  external  source  of  current. 

The  stronger  the  sulphuric  acid  in  the  clay  cells  of  the 
simple  apparatus  is,  with  the  greater  rapidity  it  acts  upon  the 
zinc  plates,  and  the  more  quickly  is  the  copper  deposited  upon 
the  moulds.  If  the  zinc  surface  of  the  clay  cells  is  very  large 
in  proportion  to  the  surface  of  the  moulds,  the  deposition  of 
copper  also  takes  plane  with  correspondingly  greater  rapidity. 
However,  a  rapid  deposition  of  copper  is  to  be  avoided,  if  de- 
posits possessing  the  above-mentioned  desirable  properties 
are  to  be  obtained,  because  a  deposit  forced  too  much,  turns 
out  incoherent,  lacking  in  density,  is  frequently  blistered,  and, 
with  too  strong  action,  is  even  pulverulent.  The  color  of  the 
deposit  furnishes  a  certain  criterion  for  its  quality ;  a  red- 
brown  color  indicating  an  unsuitable  deposit,  and  a  beautiful 
rose  color  a  good  serviceable  one. 

One  part  of  concentrated  sulphuric  acid  of  66°  Be.  to  30  of 
water  has  formerly  been  given  as  the  proper  proportions  for 
the  dilute  acid  used  for  filling  the  clay  cells,  provided  the  zinc 


3/6  ELECTRO-DEPOSITION    OF    METALS. 

surface  be  about  the  same  as  that  of  the  moulds.  If  the  zinc 
surface  is  smaller  than  that  of  the  moulds,  stronger  acid  may 
be  used ;  but  if  it  is  larger,  the  acid  will  have  to  be  more 
dilute.  The  correct  concentration  of  the  acid  in  the  clay  cells 
may  be  readily  determined  by  the  progressive  result  of  the  de- 
posit and  its  color.  Deep  moulds  require  a  stronger  current, 
and  hence  acid  of  greater  strength  than  flat  moulds ;  however, 
if  after  such  deep  moulds  are  provided  with  a  preliminary 
deposit,  the  current  proves  too  strong  for  the  correct  progress 
of  the  operation,  its  action  may  be  weakened  by  either  dilut 
ing  the  acid  in  the  clay  cells  with  water,  or  by  taking  out  a 
few  zinc  plates,  or  by  hanging  a  few  copper  sheets  upon  the 
object- rods,  or  suspending  more  moulds. 

For  the  deposition  of  copper  with  a  separate  source  of  current 
(battery  or  dynamo),  the  same  that  has  been  said  above  applies 
as  regards  the  current-strength,  which  must  be  brought  to  a 
suitable  degree  by  the  resistance  board.  The  most  suitable 
current-density  for  the  production  of  a  good  deposit  is  1.5  to  2 
amperes  per  1^/4  square  inches  of  surface  of  moulds  for  baths 
for  depositions  with  a  separate  source  of  current,  given  on  page 
362,  if  at  rest,  and  2  to  3  amperes  if  in  motion. 

Since  even  for  deeper  moulds  a  tension  of  1.5  volts  suffices,  if 
the  bath  is  acidulated,  the  more  powerful  Bunsen  elements  will 
have  to  be  coupled  alongside  one  another,  but  two  of  the 
weaker  Daniell  or  Lallande  elements  one  after  the  other,  and  of 
such  groups,  as  many  as  are  required  will  have  to  be  coupled 
alongside  one  another  for  quantity  of  current  (see  page  20),  to 
make  the  active  zinc  surface  nearly  equal  to  that  of  the  moulds. 
However,  for  flat  moulds  coupling  the  separate  weaker  elements 
alongside  one  another  is  also  sufficient.  When  the  moulds  are 
coated  with  copper  on  every  side,  and  also  the  deeper  portions, 
the  current  is  weakened  if  a  copper  deposit  of  pulverulent  or 
coarse-grained  structure  and  of  a  dark  color  should  appear  on 
the  edges  of  the  moulds,  and  it  is  feared  that  the  deposit  upon 
the  design  or  type  might  also  turn  out  pulverulent.  The  cur- 
rent, however,  should  only  be  sufficiently  weakened  to  prevent 


GALVANOPLASTY  (REPRODUCTION).          377 

a  further  progress  of  the  dark  deposit  on  the  edges  towards  the 
interior  of  the  surface  of  the  mould.  If,  however,  by  too  strong 
a  current  the  separation  of  a  pulverulent  deposit  upon  the  de- 
sign has  already  taken  place,  the  deposit  may  generally  be 
saved;  if  the  fact  is  noticed  in  time,  and  the  current  correspond- 
ingly weakened,  as  the  layers  are  firmly  united  by  the  coherent 
copper  then  deposited. 

The  current  of  the  dynamo-machine  must  also  be  sufficiently 
weakened  by  the  resistance  board  in  front  of  the  bath,  or  by 
that  of  the  machine  to  guarantee  the  good  quality  of  the  deposit. 
For  deeper  moulds  the  tension  for  covering  may  amount  to  I 
or  1.5  volts,  and  for  very  deep  and  steep  moulds  to  1.5  or  2 
volts.  But  when  the  moulds  are  completely  covered  the  cur- 
rent is  reduced  to  about  0.75  volt,*  and  the  operation  finished 
with  this  tension. 

.  The  average  time  required  for  the  production  of  a  sufficiently 
heavy  deposit  with  the  dynamo-machine  is  from  7  to  8  hours. 
In  this  time  the  deposit  acquires  a  thickness  of  about  ^  milli- 
metre (0.013  inch),  which  corresponds  to  a  weight  of  about  25 
grammes  (14.11  drachms)  of  copper  per  15^  square  inches. 

Now,  since  it  frequently  happens  that  an  electrotype  has  to 
be  finished  and  delivered  in  a  hurry,  the  work  may  have  to  be 
continued  during  the  night;  but  as  it  may  not  be  desirable  to 
have  the  dynamo  running,  either  a  cell  apparatus  or  accumu- 
lators have  to  be  employed.  In  using  a  cell  apparatus,  it  is 
advisable  to  first  quickly  coat  the  moulds  by  the  current  of  the 
dynamo,  and  then  finish  the  deposit  in  the  apparatus. 

In  modern  times  accumulators  have  been  successfully  used 
for  the  same  purpose. 

A  detailed  description  of  the  accumulators  and  directions 
for  their  treatment  may  here  be  omitted,  they  being  furnished 
by  the  manufacturers  of  the  various  systems.  Each  accumu- 
lator consists  of  a  number  of  alternately  positive  and  negative 
lead  plates  immersed  in  a  vessel  filled  with  dilute  sulphuric 

*  These  current-strengths  refer  to  formulae  I.  and  II.  given  on  page  362. 


3/8  ELECTRO-DEPOSITION    OF   METALS. 

acid.  By  conducting  the  current  of  a  dynamo-machine  into 
the  accumulator  so  that  the  positive  current  passes  into  the 
positive  plates,  and  the  negative  current  into  the  negative 
plates,  lead  peroxide  is  formed  upon  and  in  the  porous  posi- 
tive plates  by  the  co-operation  of  the  sulphuric  acid  and  the 
oxygen  appearing  on  the  positive  pole,  and  the  greater  the 
quantity  of  lead  peroxide  thus  formed,  the  more  electricity  is 
stored  in  the  accumulators.  These  operations  are  called  charg- 
ing the  accumulator.  By  interrupting  the  introduction  of  a 
current  and  closing  the  circuit  of  the  positive  and  negative 
plate  systems  by  the  introduction  of  electrodes  in  an  electro- 
lyte (galvanic  bath),  a  current  is  developed  whereby  the  lead 
peroxide  of  the  positive  plates  which  has  been  formed  is  re- 
duced to  lead,  while  the  negative  plates  are  oxidized  to  lead 
peroxide.  This  process  is  termed  discharging.  The  chemical 
processes  appearing  thereby  are  of  more  complicated  nature 
than  here  given,  but  are  omitted  so  as  to  render  comprehension 
of  the  process  less  difficult  The  directions  for  charging  and 
discharging  the  accumulator  must  be  strictly  followed,  and  re- 
quire great  attention,  as  charging  with  too  strong  a  current,  or 
a  too  abundant  discharge  may  cause  the  rapid  destruction  of 
the  plates.  The  charging  is  best  done  during  the  day  with  a 
special  small  dynamo. 

The  electro-chemical  process  of  forming  storage  batteries, 
although  discovered  in  Europe  many  years  ago,  has  only  been 
developed  during  the  last  six  or  eight  years.  Since  then  it 
has  constantly  been  growing  in  favor  until  now,  as  made  in 
this  country,  the  electro-chemically  formed  storage  battery  has 
strength  through  the  proper  adjustment  of  its  mechanical 
parts,  durability  by  reason  of  the  quantity  and  quality  of 
material  used  therein,  high  efficiency  through  the  purely 
electro-chemical  action  given  by  a  special  process,  and  large 
capacity  for  its  weight  by  reason  of  the  deep  and  thorough 
formation  of  the  active  material. 

The  diagram,  Fig.  134,  shows  the  connections  of  a  plant  as 
installed  by  the  Electro-Chemical  Storage  Battery  Co.,  of  New 
York  City. 


VERSITT 


GALVANOPLASTY    (REPRODUCTION). 
FIG.  134. 


379 


380  ELECTRO-DEPOSITION    OF   METALS. 

By  suitable  manipulation  of  the  switches  and  rheostats  it  is 
possible  to  make  the  following  connections:  i.  The  dynamo 
alone  can  be  used  on  the  baths.  2.  The  batteries  alone  can  be 
used  on  the  baths.  3.  The  dynamo  can  be  used  on  the  baths 
and  the  batteries  charged  with  the  excess-current,  while  at  the 
same  time  steadying  the  dynamo  current.  4.  The  dynamo 
and  batteries  can  be  used  in  multiple  on  the  baths,  giving  a 
greatly  increased  capacity. 

Detaching  the  deposit  from  the  mould. — When  the  mould  has 
received  a  suitable  deposit,  it  is  taken  from  the  bath,  rinsed  in 
water,  and  all  edges  which  might  obstruct  the  detachment  of  the 
deposit  from  the  mould  are  removed  with  a  knife.  From  gutta- 
percha  moulds  the  deposit  is  gradually  lifted  by  inserting  under 
one  corner  a  flat  horn  plate  or  a  thin  dull  brass  blade  and  ap- 
plying a  very  moderate  pressure ;  particles  of  gutta-percha 
which  may  remain  adherent  are  carefully  burnt  off  over  a  flame. 
Wax  moulds  are  placed  in  an  inclined  position,  and  a  stream  of 
hot  water  is  poured  over  the  copper  surface,  by  which  means 
the  wax  is  sufficiently  softened  to  allow  the  shell  of  copper  to 
be  stripped  off.  This  may  be  done  by  taking  hold  of  one  cor- 
ner of  the  shell  and  quickly  lifting  it  as  the  hot  water  flows  over 
it.  In  removing  the  shell  care  should  be  taken  to  keep  it 
straight,  as  otherwise  it  will  be  difficult  to  back  and  finish  it 
properly. 

Backing  the  deposit  or  shell. — The  tinning  of  the  back  of  the 
shell  is  the  next  operation,  and  has  for  its  object  to  strengthen 
the  union  between  the  shell  and  the  backing  metal.  For  this 
purpose  the  back  of  the  shell  is  cleansed  by  brushing  with 
''soldering  fluid,"  made  by  allowing  muriatic  acid  to  take  up 
as  much  zinc  as  it  will  dissolve,  and  diluting  with  about  J^  of 
water,  to  which  some  sal  ammoniac  is  sometimes  added.  Then 
the  shell,  face  down,  is  heated  by  laying  it  upon  an  iron  solder- 
ing plate,  floated  on  a  bath  of  melted  stereotype  metal,  and, 
when  hot  enough,  melted  solder  (half  lead  and  half  tin)  is 
poured  over  the  back,  which  gives  it  a  clean,  bright,  metallic 
covering.  Or,  the  shell  is  placed  downward  in  the  backing- 


GALVANOPLASTY  (REPRODUCTION).          381 

pan,  brushed  over  the  back  with  the  soldering  fluid,  alloyed 
tinfoil  spread  over  it,  and  the  pan  floated  on  the  hot  backing 
metal  until  the  foil  melts  and  completely  covers  the  shell. 
When  the  foil  is  melted  the  backing  pan  is  swung  on  to  a 
leveling  stand,  and  the  melted  backing  metal  is  carefully 
poured  on  the  back  of  the  shell  from  an  iron  ladle,  commenc- 
ing at  one  of  the  corners  and  gradually  running  over  the  sur- 

FIG.  135. 


face  until  it  is  covered  with  a  backing  of  sufficient  thickness. 
Another  method  is  as  follows :  After  tinning  the  shell  it  is 
allowed  to  take  the  temperature  of  the  backing  metal  on  the 
floating  iron  plate.  The  plate  is  then  removed  from  the  melted 
metal,  supported  in  a  level  position  on  a  table  having  project- 
ing iron  pins  on  which  it  is  rested,  and  the  melted  stereotype 
metal  is  carefully  ladled  to  the  proper  thickness  on  the  back  of 


382 


ELECTRO-DEPOSITION    OF   METALS. 


the  tinned  shell.  This  process  is  called  "  backing."  The 
thickness  of  the  metal-backing  is  about  an  eighth  of  an  inch. 
A  good  composition  for  backing  metal  consists  of  lead  90 
parts,  tin  5,  and  antimony  5. 

Finishing. — For  this  purpose  the  plates  go  first  to  the  saw 
table  (Fig.  135),  for  the  removal  of  the  rough  edges  by  means 
of  a  circular  saw.  The  plates  are  then  shaved  to  take  off  any 

FIG.  136. 


roughness  from  the  back  and  make  them  of  even  thickness. 
In  large  establishments  this  portion  of  the  work,  which  is  very 
laborious,  is  done  with  a  power  planing  or  shaving  machine, 
types  of  which  are  shown  in  Figs.  136  and  137,  Fig.  136  being 
a  shaving  machine  with  steam  one  way,  and  Fig.  137  one  with 


GALVANOPLASTY  (REPRODUCTION). 


383 


steam  both  ways.  The  flatness  of  the  plates  is  then  tested  with 
a  straight  edge  and  any  unevenness  rectified  by  gentle  blows 
with  a  polished  hammer,  taking  every  care  that  the  face  be  not 
damaged.  The  plate  then  passes  to  the  hand  shaving  machine, 
where  the  back  is  shaved  down  to  the  proper  thickness,  smooth 
and  level.  The  edges  of  the  plate  are  then  planed  down  square 
and  to  a  proper  size,  and  finally  the  plates  are  mounted  on 
wood  type-high.  Book-work  is  generally  not  mounted  on 


FIG.  137 


wood,  the  plates  being  left  unmounted  and  finished  with 
beveled  edges,  by  which  they  are  secured  on  suitable  plate- 
blocks  of  wood  or  iron  supplied  with  gripping  pieces,  which 
hold  them  firmly  at  the  proper  height  and  enable  them  to  be 
properly  locked  up. 

Finally,  it  remains  to  say  a  few  words  about  the  process  by 
which  a  copy  may  be  directly  made  from  a  metallic  surface 
without  the  interposition  of  wax  or  gutta-percha.  If  the  me- 


384  ELECTRO-DEPOSITION    OF    METALS. 

tallic  surface  to  be  moulded  were  free  from  grease  and  oxide, 
the  deposit  would  adhere  so  firmly  as  to  render  its  separation 
without  injury  almost  impossible.  Hence,  the  metallic  original 
must  first  undergo  special  preparation,  so  as  to  bring  it  into  a 
condition  favorable  to  the  detachment  of  the  deposit.  This  is 
done  by  thoroughly  rubbing  the  original  with  an  oily  rag,  or, 
still  better,  by  lightly  silvering  it  and  exposing  the  silvering  for 
a  few  minutes  to  an  atmosphere  of  sulphuretted  hydrogen, 
whereby  sulphide  of  silver  is  formed,  which  is  a  good  conduc- 
tor, but  prevents  the  adherence  of  the  deposit  to  the  original. 
For  the  purpose  of  silvering,  free  the  surface  of  the  metallic 
original  (of  brass,  copper,  or  bronze)  from  grease,  and  pickle 
it  by  washing  with  dilute  potassium  cyanide  solution  (i  part 
potassium  cyanide  to  20  water.)  Then  brush  it  over  with  a 
solution  of  4^  drachms  of  nitrate  of  silver  and  I  oz.  6  drachms 
of  potassium  cyanide  (98  per  cent.)  in  one  quart  of  water;  or, 
still  better,  immerse  the  original  for  a  few  seconds  in  this  bath, 
until  the  surface  is  uniformly  coated  with  a  film  of  silver.  The 
production  of  the  layer  of  sulphide  of  silver  is  effected  accord- 
ing to  the  process  described  later  on  (p.  393).  The  negative 
thus  obtained  is  also  silvered,  made  yellow  with  sulphuretted 
hydrogen,  and  a  deposit  of  copper  is  then  made,  which  repre- 
sents an  exact  copy  of  the  original.  Instead  of  sulphurizing 
the  silvering  with  sulphuretted  hydrogen,  it  may  also  be  iodized 
by  washing  with  dilute  solution  of  iodine  in  alcohol.  The 
washed  plate,  prior  to  bringing  it  into  the  copper  bath,  is  for 
some  time  exposed  to  the  light. 

To  prevent  the  separation  of  copper  on  the  back  of  the  me- 
tallic original  to  be  copied,  it  is  coated  with  asphalt  lacquer, 
which  must  be  thoroughly  dry  before  bringing  into  the  bath. 
When  the  deposit  of  copper  is  of  sufficient  thickness,  the  plate 
is  taken  from  the  bath,  rinsed  in  water,  and  dried.  The  edges 
are  then  trimmed  off  by  filing  or  cutting  to  facilitate  the  sepa- 
ration of  the  shell  from  the  original. 

Of  course  only  metals  which  are  not  attacked  by  the  acid 
copper  solution  can  be  directly  brought  into  the  bath.  Steel 


GALVANOPLASTY  (REPRODUCTION).          385 

plates  must  therefore  first  be  thickly  coppered  in  the  alkaline 
copper  bath,  and  even  this  precaution  does  not  always  protect 
the  plate  from  corrosion.  It  is  therefore  better  to  produce  in 
a  silver  bath  (formula  L,  p.  249)  a  copy  in  silver  of  sufficient 
thickness  to  allow  of  the  separation  of  both  plates.  The  silver 
plate  is  iodized,  and  from  it  a  copy  in  copper  is  made  by  the 
galvanoplastic  process.  The  copper  plate  thus  obtained  is  an 
exact  copy  of  the  original,  and  after  previous  silvering,  the 
desired  number  of  copies  may  be  made  from  it. 

Electro-etching. — The  lines  produced  by  the  ordinary  process 
of  etching  actually  represent,  when  viewed  under  the  micro- 
scope, a  continuous  series  of  irregular  depressions  and  small 
cavities,  and  when  some  depth  is  required  they  are  apt  to  be 
corroded  underneath,  and  to  increase  so  much  in  width  that  the 
plates  are  frequently  spoiled.  None  of  these  objections  applies 
to  the  galvanic  process  of  etching,  which  is  the  invention  of 
Thomas  Spencer.  Each  line,  when  viewed  under  the  micro- 
scope, represents  a  perfect  furrow,  and  is  just  rough  enough — 
for  instance,  in  the  preparation  of  printing  plates — to  hold  the 
printing  ink.  Lines  of  considerable  depth  may  be  produced 
without  the  danger  of  extending  in  width  or  corroding  under- 
neath. The  corners  of  the  intersection  of  two  lines  are  as 
sharp  as  if  the  lines  were  engraved.  A  chief  requisite  for 
electro-etching  is  a  good  etching  ground,  since  it  may  fre- 
quently happen  that  the  latter  may  answer  very  well  for  the 
ordinary  process,  but  is  not  capable  of  offering  sufficient  re- 
sistance to  the  electric  current.  A  great  advantage  in  electro- 
etching  is  that  the  solvent  is  always  of  the  same  strength,  and, 
therefore,  constant  in  its  action,  and  that  there  is  no  evolution 
of  acid  vapors  which  are  injurious  to  the  respiratory  organs. 

The  operation  of  electro-etching  is  conducted  as  follows :  A 
conducting  wire  is  soldered  with  tin  solder  to  the  object,  and 
the  latter  is  then  coated  with  the  etching  ground.  The  design 
is  then  traced  with  a  graver,  taking  care  that  the  tool  lays  bare 
the  metal  in  all  the  lines.  The  object  thus  prepared  is  con- 
nected with  the  positive  pole  and  suspended  in  the  bath,  while 
25 


386  ELECTRO-DEPOSITION    OF   METALS. 

a  plate  of  the  same  metal  as  the  object  is  secured  to  the  nega- 
tive pole.  The  bath  consists  of  a  dilute  acid  corresponding 
to  the  metal  of  the  object.  For  silver,  dilute  nitric  acid  is  used  ; 
for  gold  and  platinum,  water  acidulated  with  aqua  regia ;  for 
copper,  brass,  and  zinc,  water  acidulated  with  sulphuric  acid  ; 
and  for  tin,  water  acidulated  with  hydrochloric  acid.  Baths 
containing  the  metal  to  be  etched  in  solution,  however,  work 
better  than  acids  diluted  with  water.  Thus,  for  gold  and 
platinum,  chloride  of  gold  and  platinic  chloride  are  used  ;  for 
silver,  solution  of  nitrate  of  silver ;  for  copper  and  brass,  solu- 
tion of  blue  vitriol ;  for  iron  and  steel,  solution  of  green  vitriol, 
or  of  ammonium  chloride,  or  a  combination  of  both ;  for  zinc, 
solution  of  white  vitriol  or  of  chloride  of  zinc,  etc.  There  are 
besides  various  metallic  salts  suitable  for  etching  by  themselves 
or  in  combination  with  the  above-named  salts. 

As  etching  ground  various  compositions  may  be  employed, 
it  being,  however,  best  to  use,  if  possible,  one  which  can  be 
readily  removed.  A  mixture  of  equal  parts  of  asphalt  and 
copal  varnish  forms  a  good  etching  ground  ;  also  a  composi- 
tion obtained  by  melting  together  asphalt  2j^  parts,  wax  2, 
rosin  I,  and  black  pitch  2.  However,  the  following  composi- 
tion, which  resists  25  per  cent,  nitric  acid,  is  to  be  preferred. 
It  is  prepared  as  follows :  Melt  yellow  wax  4  parts,  Syrian 
asphalt  4,  black  pitch  I,  and  white  Burgundy  pitch  I.  When 
the  mixture  boils  gradually  add,  with  constant  stirring,  4  parts 
more  of  pulverized  Syrian  asphalt.  Continue  boiling  until  a 
sample  poured  upon  a  stone  and  allowed  to  cool  breaks  in 
bending.  Then  pour  the  mixture  into  cold  water  and  shape  it 
into  small  balls,  which  for  use  are  dissolved  in  oil  of  turpentine. 

Since  the  current- strength  is  under  perfect  control,  the  etch- 
ing may  be  carried  to  any  depth  desired.  Some  portions  may 
be  less  etched  than  others  by  taking  the  plate  from  the  bath, 
and,  after  washing  and  drying,  coating  the  portions  which  are 
not  to  be  further  etched  with  lacquer,  and  returning  the  plate 
to  the  bath. 

Printing  plates  on  relief  may  in  this  manner  be  prepared  by 


GALVANOPLASTY  (REPRODUCTION).          387 

slightly  etching  the  bared  design  of  a  copper-plate  in  the  gal- 
vanoplastic  copper  bath,  and  then  bringing  the  plate  as  object 
in  contact  with  the  negative  pole,  while  a  plate  of  chemically 
pure  copper  serves  as  anode.  The  deposited  copper  unites 
firmly  with  the  rough  copper  of  the  etched  plates,  and  after  re- 
moving the  etching-ground  with  benzine  or  oil  of  turpentine 
the  design  appears  in  relief. 

Heliography. — By  this  term  are  understood  several  methods 
of  printing,  in  which  plates  of  asphalt,  chrome  gelatine,  etc., 
produced  by  exposure  to  light,  are  used.  For  our  purposes 
only  the  method  is  of  interest  by  which  from  the  negative,  pro- 
duced by  the  action  of  light,  a  galvanoplastic  reproduction — 
printing  plates  in  high  and  low  relief — in  metal  is  made.  The 
heliographic  process  invented  by  Pretsch  and  improved  by 
Scamoni,  consists  in  taking  by  photography  a  good  negative  of 
the  engraving  or  other  object  to  be  reproduced,  developing 
with  green  vitriol,  reinforcing  with  pyrogallic  acid  and  silver 
solution,  and  then  fixing  with  sodium  hyposulphite  solution  in 
the  same  manner  as  customary  for  photographic  negatives.  A 
further  reinforcement  with  chloride  of  mercury  solution  then 
takes  place  until  the  layer  appears  light  gray.  Now  wash 
thoroughly  and  intensely  blacken  the  light  portions  by  pouring 
upon  them  dilute  potassium  cyanide  solution.  As  in  the  photo- 
graphic process,  the  solutions  must  be  applied  in  abundance 
and  without  stopping,  as  otherwise  streaks  and  stains  are 
formed.  After  washing,  the  plate  is  dried,  further  reinforced, 
and  finally  coated  with  colorless  negative  varnish.  From  this 
negative  a  positive  collodion  picture  is  taken,  which  is  in  the 
same  manner  developed,  reinforced,  and  fixed,  the  reinforce- 
ment with  pyrogallic  acid  being  continued  until  the  picture  is 
quite  perceptibly  raised.  After  careful  washing,  pour  upon  the 
plate  quite  concentrated  chloride  of  mercury  solution,  which 
has  to  be  frequently  renewed,  until  the  picture,  at  first  deep 
black,  acquires  a  nearly  white  color,  and  the  lines  are  percept- 
ibly strengthened.  Now  wash  with  distilled  water,  next  with 
dilute  potassium  iodide  solution,  and  finally  with  ammoniacal 


388  ELECTRO-DEPOSITION   OF    METALS. 

water,  whereby  the  picture  acquires  first  a  greenish,  then  a 
brown,  and  finally  a  violet-brown  color.  After  draining,  the 
plate  may  progressively  be  treated  with  solutions  of  platinum 
chloride,  gold  chloride,  green  vitriol,  and  pyrogallic  acid,  the 
latter  exerting  a  solidifying  effect  upon  the  pulverulent  metallic 
deposits.  The  metallic  relief  is  now  ready ;  the  layer  is  slowly 
dried  over  alcohol,  and  the  plate,  when  nearly  cold,  quickly 
coated  with  a  thin  rosin  varnish,  which,  after  momentary  dry- 
ing, remains  sufficiently  sticky  to  retain  a  thin  layer  of  black 
lead,  which  is  applied  with  a  tuft  of  cotton.  The  edge  of  the 
plate  is  finally  surrounded  with  wax,  and,  after  being  wired,  the 
plate  is  brought  into  the  galvanoplastic  copper  bath  to  be  re- 
produced. 

Galvanoplastic  reproduction  of  busts,  vases,  etc. — For  this  pur- 
pose an  entirely  different  process  of  preparing  the  moulds  than 
that  described  for  electrotyping  is  required,  the  material  for 
moulding  depending  on  the  nature  of  the  original.  Besides 
gutta-percha  and  wax,  readily  fusible  metals,  plaster  of  Paris, 
and  glue  will  have  to  be  considered.  If  the  original  bears  heat- 
ing to  about  230°  F.,  a  copy  in  one  of  the  readily  fusible  alloys 
given  later  on  may  be  made ;  if  it  will  stand  heat  and  pressure, 
it  is  best  to  mould  in  gutta-percha;  but  if  neither  heat  nor 
pressure  can  be  applied,  the  moulds  will  have  to  be  executed 
in  plaster  of  Paris  or  in  glue.  The  manner  of  moulding  and 
the  material  to  be  chosen  furthermore  depend  on  whether 
surfaces  in  high  relief  or  round  plastic  bodies  are  to  be  copied, 
whether  projecting  portions  are  undercut,  and  whether  the 
mould  can  be  directly  detached,  or,  if  this  is  not  the  case, 
whether  the  original  has  to  be  dissected  and  moulded  in  sepa- 
rate parts. 

Regarding  the  practice  of  moulding,  the  reader  is  referred  to 
special  works  on  that  subject;  only  the  main  points  for  the 
most  frequently  occurring  reproductions  will  here  be  given. 

Surfaces  in  relief  and  not  undercut  are  readily  moulded  in  an 
elastic  mass  such  as  gutta-percha  or  wax ;  however,  undercut 
reliefs  and  especially  round  plastic  objects  mostly  require  a 


GALVANOPLASTY  (REPRODUCTION).          389 

plaster-of- Paris  mould  and  are  generally  dissected ;  the  dis- 
section being  of  course  not  carried  further  than  absolutely 
necessary,  because  the  separate  parts  must  be  united  by  a 
soldering  seam  which  requires  careful  work,  and  the  seam 
itself  must  be  worked  over  and  made  invisible.  Hence  the 
section  should  as  much  as  possible  be  made  through  smooth 
surfaces,  edges,  etc.,  where  the  subsequent  union  by  a  solder- 
ing seam  will  prove  least  troublesome,  while  cutting  through 
ornaments  or  through  portions,  the  accurate  reproduction  of 
which  is  of  the  utmost  importance,  should  be  avoided.  Heads 
and  busts  are  always  executed  in  a  core  mould  and  in  portions 
unless  the  entire  figure  is  to  be  deposited  in  one  piece  in  a 
closed  mould.  The  section  is  made  either  through  the  centre 
line  of  the  head  through  the  lose,  which,  however,  makes  the 
subsequent  union  very  troublesome,  if  the  copy  is  to  be  an 
exact  reproduction  of  the  original,  or  the  mould  is  divided 
from  ear  to  ear,  which  has  the  disadvantage  that  the  deepest 
part  of  the  mould  corresponding  to  the  nose  receives  the 
thinnest  deposit.  It  has,  therefore,  been  proposed  to  make 
two  cuts  so  that  three  portions  are  formed ;  one  cut  from  one 
ear  at  the  commencement  of  the  growth  of  hair  to  the  other 
ear ;  and  the  second  cut  from  one  ear  in  a  downward  direction 
below  the  lower  jaw  in  the  joint  of  the  head  and  neck,  through 
this  joint  below  the  chin,  and  then  upwards  to  the  other  ear, 
and  in  front  of  it  to  where  the  hair  begins.  In  bearded  male 
heads  the  cut  follows  the  contour  of  the  beard  and  not  the 
joint  on  the  neck  behind  the  beard. 

To  mould  round  articles  in  gutta-percha,  the  softened  gutta- 
percha  is  kneaded  with  wet  hands  upon  the  oiled  original,  or, 
in  order  to  avoid  some  portions  receiving  a  stronger  pres- 
sure than  others,  and  to  insure  a  layer  of  gutta-percha  of  uni- 
form thickness  upon  all  portions,  the  moulding  may  also  be 
executed  in  a  ring  or  frame  of  iron  or  zinc  under  a  press. 
For  the  rest,  all  that  has  been  said  in  regard  to  moulding  in 
gutta-percha  on  p.  367  is  also  applicable. 

The  following  metallic  alloys  have  been  proposed  for  the 
preparation  of  moulds  : — 


390  ELECTRO-DEPOSITION    OF   METALS. 

I.  Lead  2  parts,  tin  3,  bismuth  5  ;   fusible  at  212°  F. 
II.  Lead  5,  tin  3,  bismuth  8;   fusible  at  185°  F. 

III.  Lead  2,  tin  2,  bismuth  5,  mercury  I  ;   fusible  at  158°  F. 

IV.  Lead  5,  tin  3,  bismuth  5,  mercury  2  ;    fusible  at  127.5°  F. 
The    advantage    of   metallic  moulds    consists  in    the    metal 

being  a  good  conductor  of  electricity,  in  consequence  of  which 
heavy  deposits  of  greater  uniformity  can  be  produced  than 
with  non-metallic  moulds  which  have  been  made  conductive 
by  black  lead.  Nevertheless,  they  are  but  seldom  employed, 
on  account  of  the  crystalline  structure  of  the  alloys  and  the 
difficulty  of  avoiding  the  presence  of  air  bubbles.  Bottger 
claims  that  a  mixture  of  lead  8  parts,  tin  3,  and  bismuth  8, 
which  is  fusible  at  227°  F.,  shows  a  less  coarse-grained 
structure. 

Fusible  alloys  containing  mercury  should  not  be  used  for 
taking  casts  of  metallic  objects — iron  excepted — as  these  will 
amalgamate  with  the  mercury  and  be  injured.  Moreover, 
copper  deposits  obtained  upon  such  alloys  are  very  brittle, 
which  is  due  to  the  combination  of  the  mercury  with  the  de- 
posited copper. 

For  moulding  with  metallic  alloys  place  the  oiled  object  at 
the  bottom  of  a  flat  vessel  and  pour  the  liquid  metal  upon  it; 
or  pour  the  liquid  metal  into  a  box,  remove  the  layer  of  oxide 
with  a  piece  of  stout  paper,  and  when  the  metal  is  just  begin- 
ning to  congeal  firmly  press  the  object  in  it. 

Plaster  of  Paris  is  used  for  making  casts  of  portions  from 
originals  which  are  so  strongly  undercut  that  a  mould  consist- 
ing of  one  piece  could  not  be  well  detached  from  them.  For 
taking  casts  from  metallic  coins  and  medals  or  from  small 
plaster  reliefs,  it  is  a  very  convenient  material.  The  mode  of 
procedure  is  as  follows :  After  the  original  model,  say  a  medal, 
has  been  thoroughly  soaped  or  black-leaded,  wrap  round  the 
rim  a  piece  of  sufficiently  stout  paper  or  thin  lead  foil,  and 
bind  it  in  such  a  manner  by  means  of  sealing-wax  that  the 
face  of  the  medal  is  at  the  bottom  of  the  receptacle  thus 
formed.  Then  place  the  whole  to  a  certain  depth  in  a  layer 


GALVANOPLASTY  (REPRODUCTION).          39 1 

of  fine  sand,  which  prevents  the  escape  of  the  semi-fluid  plaster 
of  Paris  between  the  rim  of  the  medal  and  the  paper.  Now 
mix  plaster  of  Paris  with  water  to  a  thin  paste,  take  up  a  small 
quantity  of  this  paste  with  a  pencil  or  brush  and  spread  it  in  a 
thin  film  carefully  and  smoothly  over  the  face  of  the  medal, 
then  pour  on  the  remainder  of  the  paste  up  to  a  proper  height 
and  allow  it  to  set.  After  a  few  minutes  the  plaster  heats  and 
solidifies.  Then  remove  the  surrounding  paper,  scrape  off 
with  a  knife  what  has  run  between  the  paper  and  the  rim  of 
the  medal,  and  carefully  separate  the  plaster  cast  from  the 
model.  If  instead  of  applying  the  first  layer  with  a  brush,  the 
whole  of  the  plaster  were  run  at  once  into  the  receptacle,  there 
would  be  great  risk  of  imprisoning  air  bubbles  between  the 
model  and  the  mould,  which  would  consequently  be  worthless. 
The  mould  is  finally  made  impervious  and  conductive  accord- 
ing to  one  of  the  methods  to  be  described  later  on. 

The  moulding  in  plaster  of  Paris  in  portions,  when  casts  from 
large  plastic  objects  with  undercut  surfaces  and  reliefs  are  to  be 
taken,  is  troublesome  work,  because  each  separate  mould  must 
not  only  be  so  that  it  can  be  readily  separated  without  injury 
to  the  original,  but  must  also  fit  closely  to  its  neighbors. 
Hence  thought  and  judgment  are  required  to  see  of  which  parts 
separate  moulds  are  to  be  made,  or,  in  other  words,  in  how 
many  parts  the  mould  is  to  be  made.  After  determining  on 
the  plan  of  the  work,  the  mode  of  procedure  is  as  follows :  Oil 
a  portion  of  the  object,  if  it  consists  of  metal,  or  soap  it,  if  of 
plaster  of  Paris,  marble,  wood,  etc.,  and  apply  by  means  of  a 
brush  a  thinly-fluid  paste  of  plaster  of  Paris,  taking  care  that 
no  air  bubbles  are  formed  by  the  strokes  of  the  brush.  When 
this  thin  coat  is  hard,  continue  the  application  of  plaster  of 
Paris  with  a  horn  spatula  until  the  coat  has  acquired  a  thick- 
ness of  y^  to  i  inch,  and  allow  it  to  harden.  Then  separate  the 
mould,  and  after  cutting  or  sawing  the  edges  square  and 
smooth,  replace  it  upon  the  portion  of  the  original  model  cor- 
responding to  it.  Now  oil  or  soap  the  neighboring  portions  of 
the  model,  and  at  the  same  time  the  smooth  edges  of  the  first 


392  ELECTRO-DEPOSITION    OF   METALS. 

mould  which  come  in  contact  with  the  mould  now  to  be  made, 
and  then  proceed  to  make  the  second  mould  in  precisely  the 
same  manner  as  the  first.  When  the  second  mould  is  hard, 
trim  the  edges  and  replace  it  upon  the  model ;  the  same  pro- 
cess being  continued  until  the  entire  original  model  is  repro- 
duced in  moulds  fitting  well  together.  To  prevent  the  finished 
moulds  from  falling  off,  and  to  retain  them  in  a  firm  position 
upon  the  original  model,  they  are  tied  with  lead  wire  or  secured 
with  catches  of  brass  wire  or  sheet.  When  the  moulds  of  the 
larger  portion  of  the  model,  for  instance,  one-half  of  a  statue, 
are  finished,  the  so-called  case  or  shell  is  made,  /'.  e.,  the  backs 
of  all  the  moulds  are  coated  with  a  layer  of  plaster  of  Paris 
which  holds  them  together.  This  case  is  best  made  not  too 
thin  in  order  to  attain  a  better  resisting  power. 

The  entire  model  having  been  cast  in  the  manner  above 
described,  and  the  moulds  provided  with  the  case,  the  whole  is 
completely  dried  in  an  oven. 

The  next  operation  is  to  make  the  plaster  of  Paris  impervious 
to  fluids,  as  otherwise  by  the  moulds  absorbing  the  acid  copper 
bath,  copper  would  be  deposited  in  the  pores  of  the  plaster  and 
the  moulds  be  spoiled,  while  the  copy  would  turn  out  rough 
instead  of  having  the  smooth  exterior  of  the  model.  To  render 
plaster  of  Paris  and  other  porous  substances  impervious,  they 
are  saturated  with  wax  or  stearine  or  covered  with  a  coat  of 
varnish,  the  latter  process  being  generally  employed  for  large 
moulds.  Apply  a  coat  of  thick  linseed  oil  varnish  to  the  face 
of  the  mould,  and,  after  drying,  repeat  the  process  until  the 
mould  is  thought  to  be  sufficiently  impervious.  Rendering  the 
mould  impervious  with  wax  or  stearine  is  a  better  and  more 
complete  method.  For  this  purpose  cut  a  groove  in  the  rim 
of  the  mould,  place  in  the  groove  a  brass  wire  and  twist  the 
ends,  which  must  be  long  enough  to  hold  the  mould  by.  The 
mould,  having  been  previously  dried,  is  then  dipped  into  a  bath 
of  wax  or  stearine  kept  at  a  temperature  of  from  180°  to  212° 
F.,  and  a  number  of  air  bubbles  will  escape  from  the  mould  to 
the  surface.  When  the  production  of  air  bubbles  is  consider- 


GALVANOPLASTY  (REPRODUCTION).          393 

ably  diminished,  remove  the  mould  from  the  bath,  and  lay  it 
face  up  in  a  drying  oven,  whereby  the  melting  wax  in  conse- 
quence of  its  gravity  oozes  down,  and  the  face  of  the  mould  is 
freed  from  an  excess  of  wax.  Whenever  possible,  submerging 
the  entire  mould  should  be  avoided  and  the  operation  be  con- 
ducted as  follows :  Place  the  heated  mould  in  a  vat  filled  with 
melted  wax  or  stearine,  so  that  the  face  does  not  come  in  con- 
tact with  the  wax,  but  absorbs  wax  by  capillarity  from  the  back. 

The  moulds  thus  coated  with  varnish  or  saturated  with  wax 
are  now  made  conductive  with  black-lead,  the  operation  being 
the  same  as  that  mentioned  on  p.  372.  For  many  undercut  or 
deep  portions  black-leading  is,  however,  not  sufficient,  and  re- 
course must  be  had  to  making  the  moulds  conductive  or 
metallizing  them  by  the  wet  way. 

Metallization  by  the  wet  way. — This  method  consists  in  the 
deposition  of  certain  metallic  salts  upon  the  moulds  and  their 
reduction  to  metal  or  conversion  to  conductive  sulphur  combi- 
nations. The  process  in  general  use  is  as  follows :  Apply  with 
a  brush  upon  the  mould  a  not  too  concentrated  solution  of 
nitrate  of  silver  in  a  mixture  of  equal  parts  of  distilled  water 
and  90  per  cent,  alcohol.  When  the  coat  is  dry  expose  it  in  a 
closed  box  to  an  atmosphere  of  sulphuretted  hydrogen ;  the 
latter  converts  the  nitrate  of  silver  into  sulphide  of  silver,  which 
is  a  good  conductor  of  the  current.  For  the  production  of  the 
sulphuretted  hydrogen,  place  in  the  box,  which  contains  the 
mould  to  be  metallized,  a  porcelain  plate  or  dish  filled  with 
dilute  sulphuric  acid  (i  acid  to  8  water),  and  add  five  or  six 
pieces  of  iron  pyrites  the  size  of  a  hazel-nut.  The  develop- 
ment of  the  gas  begins  immediately,  and  the  box  should  be 
closed  with  a  well-fitting  cover  to  prevent  inhaling  the  poison- 
ous gas;  if  possible,  the  work  should  be  done  in  the  open  air 
or  under  a  well- drawing  chimney.  The  formation  of  the  layer 
of  sulphide  of  silver  requires  but  a  few  minutes,  and  if  not 
many  moulds  have  to  be  successively  treated,  the  acid  is 
poured  off  from  the  iron  pyrites  and  clean  water  poured  upon 
the  latter  so  as  not  to  cause  useless  development  of  gas. 


394  ELECTRO-DEPOSITION    OF   METALS. 

It  has  also  been  recommended  to  decompose  the  silver  salt 
by  vapors  of  phosphorus  and  to  convert  it  into  phosphide  of 
silver,  a  solution  of  phosphorus  in  bisulphide  of  carbon  being 
used  for  the  purpose.  The  layer  of  silver  salt  is  moistened 
with  the  solution  or  exposed  to  its  vapors.  This  method 
possesses,  however,  no  advantage  over  the  preceding,  because, 
on  the  one  hand,  the  phosphorous  solution  takes  fire  spontan- 
eously, and,  on  the  other,  the  odor  of  the  bisulphide  of  carbon 
is  still  more  offensive  than  that  of  sulphuretted  hydrogen. 

A  somewhat  modified  method  is  given  by  Parkes  as  follows : 
Three  solutions,  A,  B,  C,  are  required.  Solution  A  is  prepared 
by  dissolving  0.5  part  of  caoutchouc  cut  up  in  fine  pieces  in  10 
parts  of  bisulphide  of  carbon  and  adding  4  parts  of  melted  wax ; 
stir  thoroughly,  then  add  a  solution  of  5  parts  of  phosphorus  in 
60  of  bisulphide  of  carbon  together  with  5  of  oil  of  turpentine 
and  4  of  pulverized  asphalt ;  then  thoroughly  shake  this  mix- 
ture, A.  Solution  B  consists  of  2  parts  by  weight  of  nitrate  of 
silver  in  600  of  water;  and  solution  C  of  10  parts  of  chloride 
of  gold  in  600  of  water.  The  mould  to  be  metalized  is  first 
provided  with  wires  and  then  brushed  over  with,  or  immersed 
in,  solution  A,  and  after  draining  off,  dried.  The  dry  mould  is 
then  poured  over  with  the  silver  solution  (B)  and  suspended 
free  for  a  few  minutes  until  the  surface  shows  a  dark  lustre.  It 
is  then  rinsed  in  water  and  treated  in  the  same  manner  with  the 
chloride  of  gold  solution  (C),  whereby  it  acquires  a  yellowish 
tone,  when,  after  drying,  it  is  sufficiently  prepared  for  the  re- 
ception of  the  deposit.  Care  must  be  taken  in  preparing  solu- 
tion A,  as  the  bisulphide  of  carbon  containing  phosphorus 
readily  takes  fire. 

Another  method  is  as  follows :  Dissolve  5  parts  by  weight  of 
wax  in  5  of  warm  oil  of  turpentine,  and  add  to  the  solution  a 
mixture  of  5  parts  by  weight  of  phosphorus,  I  of  gutta-percha, 
5  of  asphalt  in  120  of  bisulphide  of  carbon.  When  both  are 
thoroughly  mixed,  add  to  the  whole  a  solution  of  4  parts  by 
weight  of  gun  cotton  in  60  of  alcohol  and  60  of  ether,  and  after 
thoroughly  shaking  allow  to  settle.  The  next  day  pour  off  the 


GALVANOPLASTY  (REPRODUCTION).          395 

clear  solution  from  the  sediment,  when  the  solution  can  at  once 
be  used.  It  is'  especially  well  adapted  for  coppering  parts  of 
plants,  leaves,  flowers,  etc. 

Another  method  of  metallization  is  as  follows :  Immerse  the 
leaves,  etc.,  in  iodized  collodion  composed  of  40  per  cent, 
alcohol  40  cubic  centimeters,  ether  60  cubic  centimeters,  potas- 
sium iodide  I  gramme,  gun  cotton  I  gramme. 

Allow  the  leaves,  etc.,  to  dry  so  that  a  firmly  adhering  layer 
is  formed.  Then  immerse  them  in  a  solution  of  10  parts  by 
weight  of  nitrate  of  silver  in  100  of  water,  whereby  a  layer  of 
iodide  of  silver  is  formed.  Now  expose  the  article  thus  treated 
for  some  time  to  the  light,  and  then  immerse  it  in  the  reduc- 
ing fluid  consisting  of  water  500  parts  by  weight,  green  vitriol 
25,  and  acetic  acid  of  1.04,  specific  gravity  25.  The  reduction 
of  silver  now  progresses  rapidly  and  the  articles  are  ready  for 
coppering.  In  employing  this  process  it  must  not  be  forgotten 
that  the  layer  of  collodion  will  not  stand  rough  usage  and, 
hence,  injury  to  it  by  touching  with  the  hands  and  careless 
placing  of  the  conducting  wire  have  to  be  avoided.  By 
operating  with  due  care,  the  results  are  very  satisfactory  and 
sure.  Instead  of  the  iodized  collodion,  a  mixture  of  equal 
parts  of  white  of  egg  and  saturated  solution  of  common  salt 
may  be  used,  the  remainder  of  the  process  being  the  same  as 
above  described. 

Metallization  by  metallic  powders. — In  some  cases  metalliza- 
tion by  metallic  powders  is  to  be  preferred  to  black- leading  or 
metallizing  by  the  wet  way.  Metallic  or  bronze  powders  are 
metals  in  a  state  of  exceedingly  fine  powder  of  which,  for 
galvanoplastic  purposes,  pure  copper  and  brass  powders  only 
are  of  interest.  Since  such  metallic  powders  adhere  badly  to 
waxed  surfaces,  the  mould  must  be  provided  with  a  well-drying 
coat  of  lacquer,  upon  which,  before  it  is  completely  dry,  the 
powder  is  scattered  or  sifted.  When  the  lacquer  is  hard  a 
smooth  surface  is  produced  by  going  over  the  mould  with  a 
soft  brush  dipped  in  the  metallic  powder,  an  excess  being  re- 
moved by  a  thin  jet  of  water. 


396  ELECTRO-DEPOSITION    OF    METALS. 

Lcnoir's  process — Galvanoplastic  method  for  originals  in  high 
relief. — Lenoir's  method  for  reproducing  statues  in  a  manner 
approaches  in  principle  to  that  of  the  foundry.  He  begins  by 
making  with  gutta-percha  a  mould  in  several  pieces,  which  are 
united  together  so  as  to  form  a  perfect  hollow  mould  of  the 
original.  This  having  been  done,  cover  all  the  parts  carefully 
with  black-lead.  Make  a  skeleton  with  platinum  wire,  follow- 
ing the  general  outline  of  the  model,  but  smaller  than  the 
mould,  since  it  must  be  suspended  in  it  without  any  point  of 
contact.  If  the  skeleton  thus  prepared  is  enclosed  in  the 
metallized  gutta-percha  mould,  and  the  whole  immersed  in  the 
galvanoplastic  bath,  it  will  be  sufficient  to  connect  the  inner 
surface  of  the  mould  with  the  negative  pole  of  the  battery,  and 
the  skeleton  of  platinum  wires  (which  should  have  no  points 
of  contact  with  the  metallized  surface  of  the  mould)  with  the 
positive  pole,  in  order  to  decompose  the  solution  of  sulphate 
of  copper  which  fills  the  mould.  When  the  metallic  deposit 
has  reached  the  proper  thickness,  the  gutta-percha  mould  is 
removed  by  any  convenient  process,  and  a  faithful  copy  of  the 
original  will  be  reproduced.  Lead  wires  may  be  substituted 
for  the  expensive  platinum  wires.  This  method  requires  a 
knowledge  of  the  moulder's  art,  so  that  good  results  can  only 
be  obtained  by  an  experienced  hand. 

Gelatine  moulds. — Under  certain  conditions  the  elasticity  of 
gelatine  allows  of  the  possibility  of  its  removal  from  undercut 
or  highly-wrought  portions  of  the  model,  when  it  reassumes 
the  shape  and  position  it  had  before  removal  therefrom.  But 
gelatine  requires  that  the  deposit  shall  be  made  rapidly,  other- 
wise it  will  swell  and  be  partially  dissolved  by  too  long  an  im- 
mersion in  the  copper  bath. 

To  make  a  good  gelatine  mould  proceed  as  follows :  Allow 
white  gelatine  (cabinet-maker's  glue)  to  swell  for  about  24 
hours  in  cold  water,  then  drain  off  the  water,  and  heat  the 
swollen  mass  in  a  water  bath  until  completely  dissolved. 
Compound  the  glue  solution  with  pure  glycerine  in  the  pro- 
portion of  5  to  10  cubic  centimetres  (0.24  to  0.3  cubic  inch) 


GALVANOPLASTY  (REPRODUCTION).          397 

of  glycerine  to  30  grammes  (1.05  ozs.)  of  gelatine,  which 
prevents  the  gelatine  from  shrinking  in  cooling.  When  some- 
what cooled  off,  apply  the  gelatine  to  the  oiled  original,  which 
must  be  surrounded  with  a  rim  of  plaster  of  Paris  or  wax,  to 
prevent  the  gelatine  from  running  off;  when  cold  lift  the  gela- 
tine mould  from  the  model.  Before  metallizing  and  suspend- 
ing in  the  copper  bath,  the  mould  has  to  be  prepared  to  resist 
the  action  of  the  latter,  as  otherwise  it  would  at  once  swell  and 
be  partially  dissolved  before  being  covered  with  the  deposit. 
This  is  effected  by  placing  the  mould  in  a  highly  concentrated 
solution  of  tannin,  which  possesses  the  property  of  making 
gelatine  insoluble. 

Brandley  gives  the  following  directions  for  preparing  gelatine 
solution  with  an  addition  of  tannin,  which  renders  the  moulds 
impervious  to  water :  Dissolve  20  parts  of  the  best  gelatine  in 
100  of  hot  water,  add  j£  part  of  tannic  acid  and  the  same  quan- 
tity of  rock  candy,  then  mix  the  whole  thoroughly,  and  pour  it 
upon  the  model. 

The  same  end  is  reached  by  making  a  mould  with  gelatine 
alone,  then  pouring  an  aqueous  solution  of  10  per  cent,  of 
bichromate  of  potassium  upon  it,  and,  after  draining,  exposing 
the  mould  to  the  action  of  the  sun. 

Another  method  is  as  follows :  Beat  into  a  quart  of  distilled 
water  the  whites  of  two  eggs,  filter,  and  cover  with  this  liquid 
the  entire  surface  of  the  gelatine  mould.  After  drying,  operate 
with  the  solution  of  bichromate  of  potassium  as  in  the  preced- 
ing. By  the  solar  action  the  coating  impregnated  with  bichro- 
mate is  rendered  insoluble. 

The  mould  must  finally  be  metallized  and,  when  in  the  bath, 
submitted  to  a  strong  current  at  the  beginning.  When  the 
entire  surface  is  covered  with  the  copper  deposit,  and  when 
swelling  is  no  longer  to  be  feared,  a  weaker  current  may  be 
used. 

In  the  following  a  few  special  uses  of  galvanoplasty  will  be 
briefly  described  :  — 

Nature  printing,  so   named  by  Mr.  v.  Auer,  Director  of  the 


398  ELECTRO-DEPOSITION    OF   METALS. 

Imperial  Printing  Office  at  Vienna,  has  for  its  object  the  gal- 
vanoplastic  reproduction  of  leaves  and  other  similar  bodies. 
The  leaf  is  placed  between  two  plates,  one  of  polished  steel,  the 
other  of  soft  lead,  and  is  then  passed  between  rollers,  which 
exert  a  considerable  pressure.  The  leaf  thus  imparts  an  exact 
impression  of  itself  and  of  all  its  veins  and  markings  to  the  lead, 
and  this  impression  may  be  electrotyped,  and  the  copper  plate 
produced  used  for  printing  in  the  ordinary  way.  Instead  of 
taking  the  impression  in  lead,  it  is  advisable  to  use  gutta-percha 
or  wax  for  delicate  objects,  which  should  previously  be  black- 
leaded  or  oiled.  In  the  same  manner  galvanoplastic  copies  of 
laces,  etc.,  may  be  obtained. 

The  process  used  by  Philipp  for  coating  laces  and  tissues  with 
copper  and  then  silvering  or  gilding,  belongs  rather  to  electro- 
plating than  to  galvanoplasty.  The  tissue  is  saturated  with 
melted  wax,  and  after  removing  the  excess  with  blotting  paper 
it  is  made  conductive  by  black-leading  with  a  brush.  It  is 
however  preferable  to  metallize  such  delicate  objects  by  the  wet 
way,  Parke's  method  being  especially  suitable  for  the  purpose, 
and  also  a  treatment  with  weak  solution  of  nitrate  of  silver  and 
pyrogallic  acid  frequently  alternated. 

Corvin  s  niello. — Corvin  has  invented  a  process  of  producing 
inlaid  work  by  galvanoplasty,  which  has  been  patented,  and  is 
the  exclusive  property  of  J.  P.  Kayser  &  Son,  of  Crefeld. 
The  process  is  as  follows:  A  matrice  of  metal  whose  surface  is 
finely  polished  is  first  made.  This  matrice  may  be  used  for  the 
production  of  numerous  duplicates  of  the  same  kind  of  object. 
The  incrustations  (mother-of-pearl,  glass,  ivory,  amber,  etc.) 
are  then  shaped  by  means  of  a  saw,  files,  and  other  tools  to  the 
form  corresponding  to  that  which  they  are  to  occupy  in  the 
design.  The  side  of  the  incrustation  which  is  laid  upon  the 
matrice  is,  as  a  rule,  smooth.  The  shaped  incrustations,  smooth 
side  down,  are  pasted  on  to  the  parts  of  the  model  they  are  to 
occupy  in  the  design.  The  latter  being  thus  produced,  the 
backs  of  the  non-metallic  laminae  are  metallized,  and  the  por- 
tions of  the  metallic  plate  left  free  are  slightly  oiled.  By  now 


GALVANOPLASTY  (REPRODUCTION).          399 

placing  the  matrice  thus  prepared  in  the  galvanoplastic  bath, 
the  copper  is  deposited  not  only  upon  the  metallic  matrice,  but 
also  upon  the  back  of  the  inlaid  pieces,  the  latter  being  firmly 
inclosed  by  the  deposited  metal.  When  the  deposited  metal 
has  acquired  the  desired  thickness  it  is  detached  from'  the 
matrice,  and  incrustations  with  the  right  side  polished  are  thus 
obtained.  The  laminae  are  more  accurately  and  evenly  laid  in 
than  would  be  possible  by  the  most  skilled  hand-work. 

Grasses,  leaves,  flowers,  etc.,  may  be  coated  with  copper  and 
then  silvered,  gilded,  or  platinized,  by  first  drying  them,  and, 
after  giving  them  a  certain  elasticity  by  placing  in  glycerine, 
metallizing  them  by  Parkes's  or  some  other  method. 

Plates  for  the  production  of  imitations  of  leather  are  now  fre- 
quently prepared.  The  demand  for  alligator  and  similar 
leathers  is  at  the  present  time  greater  than  the  supply,  and, 
therefore,  imitations  are  made  by  pressing  ox-leather,  the  plate 
being  prepared  by  galvanoplasty,  as  follows :  A  large  piece  of 
the  natural  skin  or  leather  is  made  impervious  to  the  bath  by 
repeated  coatings  with  lacquer,  and,  when  completely  dry, 
secured  with  asphalt  lacquer  to  a  copper  or  brass  plate.  The 
leather  is  then  black-leaded  and,  after  being  made  conductive 
by  copper  wire  or  small  lead  plates,  brought  into  the  copper 
bath.  When  the  copper  deposit  has  acquired  the  desired 
thickness,  the  plate  is  further  strengthened  by  backing  with 
stereotype  metal. 

To  coat  wood,  etc.,  with  a  galvanoplastic  deposit  of  copper. — 
The  absolutely  dry  objects  are  first  immersed  in  melted  wax, 
paraffine,  or  ceresine,  and  when  thoroughly  impregnated  taken 
out  and,  after  draining  off,  allowed  to  cool.  As  the  impregnat- 
ing material  contracts  in  cooling,  the  surface  of  the  object  is 
thereby  freed  from  an  excess  of  it.  For  this  reason  the  ma- 
terial used  for  impregnating  should  not  be  made  hotter  than 
absolutely  necessary,  because  the  hotter  it  is  the  stronger  the 
contraction  or  shrinkage.  However,  as  by  this  contraction  the 
edges  and  portions  of  the  surface  may  become  denuded  of  im- 
pregnating material,  and  thus  be  liable  to  be  attacked  by  the 


400  ELECTRO-DEPOSITION    OF   METALS. 

acid  copper  bath,  it  is  advisable  to  coat  the  objects,  after  cool- 
ing, with  an  acid-resisting  gutta-percha  lacquer  prepared  by 
dissolving  5  to  10  parts,  by  weight,  of  gutta-percha  cuttings  in 
a  mixture  of  50  parts  each  of  benzine  and  chloroform.  Keep 
the  solution  in  a  wide-mouthed  glass  bottle  provided  with  a 
well-fitting  cork,  and  apply  it  with  a  brush.  The  solution 
being  very  inflammable,  it  should  not  be  used  near  an  open 
flame. 

Wooden  handles  of  surgical  instruments,  etc.,  may  be  pro- 
tected from  the  attacks  of  the  acid  copper  bath  by  coating 
them  with  a  solution  of  wax  or  paraffine  in  ether,  the  latter 
after  evaporating  leaving  a  thin  layer  of  wax  upon  the  object. 

The  articles  thus  prepared  are  black- leaded  or  metallized  by 
Parkes's  or  one  of  the  methods  previously  given,  and  brought 
into  the  copper  bath. 

The  mercury  vessels  of  thermometers  for  vacuum  and  distilling 
apparatus  are  surrounded  by  a  thick  copper  deposit  to  protect 
them  from  injury  by  mechanical  force.  The  metallization  of 
glass,  porcelain,  clay,  terra-cotta,  etc.,  is  effected  in  the  same 
manner  as  above  described. 

Galvanoplastic  operations  in  iron. — Under  "  Deposition  of 
iron,"  page  341,  the  galvanoplastic  production  of  heavy  de- 
posits of  iron  has  already  been  referred  to,  it  being  there,  also, 
mentioned  that  according  to  the  researches  of  various  authors 
a  neutral  solution  of  i^  ozs.  of  ammonio- ferrous  sulphate  in  I 
quart  of  water  is  best  adapted  for  the  purpose,  whilst  Klein 
recommends  a  solution  of  equal  parts  of  ferrous  sulphate  and 
sulphate  of  magnesia.  To  obtain  any  way  successfully  an  iron 
electrotype  from  an  original,  for  instance,  from  a  copper  plate, 
which  should  previously  be  oiled  and  then  coated  by  means  of 
sulphuretted  hydrogen  with  a  thin  layer  of  sulphide  of  silver, 
the  following  conditions  have  to  be  fulfilled  :  The  bath  must 
be  kept  absolutely  neutral  according  to  one  of  the  methods 
given  on  page  342,  under  formulae  III.  and  IV.  Further,  the 
current-strength  must  be  so  regulated  that  absolutely  no  evolu- 
tion of  gas  on  the  object  is  perceptible,  and  the  distance  of  the 


GALVANOPLASTY  (REPRODUCTION).          40 1 

anodes  from  the  objects,  which  in  the  beginning  of  the  opera- 
tion may  be  I  ^  inches,  must,  according  to  Stammer,  be  grad- 
ually decreased  to  0.19  inch.  Furthermore,  in  the  beginning 
of  the  operation  the  plates  must  at  least  every  half  hour  be 
taken  from  the  bath  and  rinsed  off  with  a  strong  jet  of  water  to 
remove  adhering  bubbles,  the  same  object  being  attained  by 
others  by  brushing  the  plates  over  with  a  feather.  While  out 
of  the  bath  the  plates  must  not  be  allowed  to  dry,  as  the  fresh 
layers  would  not  adhere  to  the  places  which  have  become  dry. 
Now,  even  by  strictly  fulfilling  the  above-mentioned  conditions, 
a  faultless  electrotype  will  be  obtained  only  in  one  case  out  of 
five,  this  fact  being  mentioned  in  order  to  prevent  practical 
electro-platers  from  wasting  time  and  labor  upon  this  process, 
which  has  not  yet  been  sufficiently  investigated  and  worked 
out.  However,  the  interesting  conditions  for  the  production  of 
heavy  iron  deposits  present  a  field  of  research  and  observation 
to  those  who  need  not 'follow  galvanoplasty  fora  living.  In 
making  such  researches  it  should  be  especially  observed 
whether  useful  heavy  deposits  can  be  obtained  from  iron  baths 
in  motion. 

Galvanoplastic  operations  in  nickel. — Though  by  the  electro- 
deposition  of  nickel,  electrotypes  are  rendered  fit  for  printing 
with  metallic  colors,  which  attack  copper,  and  their  power  of 
resisting  wear  is  increased,  the  latter  advantage  can  to  the  full- 
est extent  be  obtained  only  by  a  thick  deposit.  However,  this 
always  alters  the  design  somewhat,  especially  the  fine  hatchings, 
this  being  the  reason  why  in  electro-nickeling  electrotypes  a 
deposit  of  medium  thickness  is,  as  a  rule,  not  exceeded.  If  a 
hard  nickel  surface  is  desired,  without  injury  to  the  fine  lines  of 
the  design,  the  layer  of  nickel  has  to  be  reproduced  by  galvano- 
plasty, and  the  deposit  of  nickel  strengthened  in  the  copper 
bath. 

But  upon  black-leaded  gutta-percha  or  wax  moulds  a  nickel 
deposit  can  only  be  obtained  in  fresh  baths ;  the  deposit,  how- 
ever, is  faultless  only  in  rare  cases,  it  generally  showing  holes 
in  the  depressions.  Hence  the  object^has  to  be  attained  in  a 
26 


402  ELECTRO-DEPOSITION    OF    METALS. 

round-about  way,  the  mode  of  procedure  being  as  follows : 
An  impression  of  the  original  is  taken  in  gutta-percha  or  wax, 
and  from  this  impression  a  positive  cliche  in  copper  is  made. 
The  latter  is  then  silvered,  the  silvering  iodized  as  previously 
described,  and  a  negative  in  copper  is  then  prepared  from  this 
positive.  The  negative  is  again  silvered,  iodized,  and  then 
brought  into  a  nickel  bath  where  it  receives  a  deposit  of  the 
thickness  of  stout  writing-paper ;  it  is  then  rinsed  in  water,  and 
the  deposit  immediately  strengthened  in  the  acid  copper  bath  ; 
for  the  rest  it  is  treated  like  ordinary  copper  deposits.  Nickel 
electrotypes  thus  made  are  almost  indestructible. 

Galvanoplaslic  operations  in  silver  and  gold. — The  prepara- 
tion of  reproductions  in  silver  and  gold  also  presents  many 
difficulties.  While  copper  is  separable  in  a  compact  state 
from  its  sulphate  solution,  silver  and  gold  have  to  be  reduced 
from  their  double  salt  solutions — potassium  silver  cyanide  and 
potassium  auric  cyanide.  However,'  these  alkaline  solutions 
attack  moulds  of  fatty  substances,  such  as  wax  and  stearine, 
consequently  also  plaster-of-Paris  moulds  impregnated  with 
these  substances,  as  well  as  gutta-percha  and  gelatine.  Hence, 
only  metallic  moulds  can  be  advantageously  used  except  the 
end  is  to  be  attained  in  a  roundabout  way  ;  that  is,  by  first 
coating  the  mould  with  a  thin  film  of  copper,  strengthening 
this  in  the  silver  or  gold  bath  and  finally  dissolving  the  film  of 
copper  with  very  dilute  nitric  acid. 

The  double  salt  solutions  mentioned  above  require  a  well- 
conducting  surface  such  as  cannot  be  readily  prepared  by 
black-leading,  a  further  reason  why  metallic  moulds  are  to  be 
preferred.  The  simplest  way  for  the  galvanoplastic  repro- 
duction in  gold  or  silver  of  surfaces  not  in  high  relief  or  under- 
cut, is  to  cover  the  object  with  lead,  silver,  or  gold  foil,  and 
pressing  softened  gutta-percha  upon  it;  the  foil  yields  to  the 
pressure  without  tearing  and  adheres  to  the  gutta-percha  so 
firmly  that  it  can  be  readily  separated  together  with  it.  Gal- 
vanoplastic reproductions  in  the  noble  metals  are  so  seldom 
made  in  practice  that  it  is  not  necessary  to  give  further  details. 
The  composition  of  the  baths  generally  used  is  as  follows : — 


COLORING,  PATINIZING,  OXIDIZING,  LACQUERING.         40.3 

Bath  for  galvanoplastic  operations  with  silver. — Fine  silver 
(in  the  form  of  silver  cyanide  or  chloride  of  silver)  i  ^  ozs., 
98  per  cent,  potassium  cyanide  5^  ozs.,  water  I  quart. 

Bath  for  galvanoplastic  operations  with  gold. — Fine  gold  (in 
the  form  of  neutral  chloride  of  gold)  I  oz.,  potassium  cyanide 
ozs.,  water  I  quart. 


CHAPTER  XV. 

COLORING,  PATINIZING,  OXIDIZING,  ETC.,  OF  METALS. — 
LACQUERING. 

THOUGH,  strictly  speaking,  these  operations  do  not  form  a 
part  of  a  work  on  the  electro-deposition  of  metals,  they  re- 
quire to  be  mentioned,  since  the  operator  is  frequently  forced 
to  make  use  of  one  or  the  other  method  in  order  to  furnish 
basis-metals  or  electro-deposits  in  certain  shades  of  colors 
ordered. 

By  patina  is  understood  the  beautiful  green  color  antique 
statues  and  other  art-works  of  bronze  acquire  by  long  exposure 
to  the  action  of  the  oxygen,  carbonic  aeid,  and  moisture  of  the 
air,  whereby  a  thin  layer  of  copper  carbonate  is  formed  upon 
them.  It  has  been  sought  to  accelerate  by  chemical  means  the 
formation  of  the  patina  thus  slowly  produced  by  the  influence 
of  time,  and  the  term  patinizing  has  been  applied  to  this  arti- 
ficial production  of  colors.  Without  drawing  a  strict  line  as  to 
which  processes  have  to  be  considered  as  coloring,  and  which 
as  patinizing,  the  most  approved  methods  for  changing  the 
color  of  the  metals  or  of  the  deposits  will  be  given.  . 

i.  Coloring  of  copper. — All  shades  from  the  pale-red  of  cop- 
per to  a  dark  chestnut-brown  can  be  obtained  by  superficial 
oxidation  of  the  copper.  For  small  objects  it  suffices  to  heat 
them  uniformly  over  an  alcohol  flame;  with  larger  objects  a 
more  uniform  result  is  obtained  by  heating  them  in  oxidizing 


404  ELECTRO-DEPOSITION    OF   METALS. 

fluids  or  brushing  them  over  with  an  oxidizing  paste,  the  best 
results  being  obtained  with  a  paste  prepared,  according  to  the 
darker  or  lighter  shades  desired,  from  2  parts  of  ferric  oxide 
and  I  part  of  black-lead,  or  i  part  each  of  ferric  oxide  and 
black-lead,  with  alcohol  or  water.  Apply  the  paste  as  uni- 
formly as  possible  with  a  brush  and  place  the  object  in  a  warm 
place  (oven  or  drying  chamber).  The  darker  the  color  is  to 
be  the  higher  the  temperature  must  be,  and  the  longer  it  must 
act  upon  the  object.  When  sufficiently  heated  the  dry  powder 
is  removed  by  brushing  with  a  soft  brush,  and  the  manipulation 
repeated  if  the  object  does  not  show  a  sufficiently  dark  tone. 
Finally  the  object  is  rubbed  with  a  soft  linen  rag  moistened 
with  alcohol,  or  brushed  with  a  soft  brush  and  a  few  drops  of 
alcohol  until  completely  dry,  and  then  with  a  brush  previously 
rubbed  upon  pure  wax.  The  more  or  less  dark  shade  pro- 
duced in  this  manner  is  very  warm  and  resists  the  action  of 
the  air. 

Brown  color  upon  copper  is  obtained  by  applying  to  the 
thoroughly  cleansed  surface  of  the  object  a  paste  of  verdigris 
3  parts,  ferric  oxide  3,  sal  ammoniac  I,  and  sufficient  vinegar, 
and  heating  until  the  applied  mixture  turns  black ;  the  object 
is  then  washed  and  dried.  By  the  addition  of  some  blue  vitriol 
the  color  may  be  darkened  to  chestnut-brown. 

A  brown  color  is  also  obtained  by  brushing  to  dryness  with  a 
hot  solution  of  I  part  of  potassium  nitrate,  I  of  common  salt, 
2  of  ammonium  chloride,  and  I  of  liquid  ammonia  in  95  of 
vinegar.  A  warmer  tone  is,  however,  produced  by  the  method 
introduced  in  the  Paris  Mint,  which  is  as  follows :  Powder  and 
mix  intimately  equal  parts  of  verdigris  and  sal  ammoniac. 
Take  a  heaping  tablespoonful  of  this  mixture  and  boil  it  with 
water  in. a  copper  kettle  for  about  twenty  minutes  and  then 
pour  off  the  clear  fluid.  To  give  copper  objects  a  bronze-like 
color  with  this  fluid,  pour  part  of  it  into  a  copper  pan ;  place 
the  objects  separately  in  it  upon  pieces  of  wood  or  glass,  so 
that  they  do  not  touch  each  other,  or  come  in  contact  with  the 
copper  pan,  and  then  boil  them  in  the  liquid  for  a  quarter  of 


COLORING,  PATINIZING,  OXIDIZING,  LACQUERING.         405 

an  hour.  Then  take  the  objects  from  the  solution,  rub  them 
dry  with  a  linen  cloth,  and  brush  them  with  a  waxed  brush. 

A  red-brown  color  on  copper  is  produced  in  China  by  the 
application  of  a  paste  of  verdigris  2  parts,  cinnabar  2,  sal 
ammoniac  5,  and  alum  5,  with  sufficient  vinegar,  heating  over 
a  coal  fire,  washing  and  repeating  the  process. 

According  to  Manduit,  copper  and  coppered  articles  may 
be  bronzed  by  brushing  with  a  mixture  of  castor  oil  20  parts, 
alcohol  80,  soft  soap  40,  and  water  40.  This  mixture  pro- 
duces tones  from  bronze  Barbedienne  to  antique  green  patina, 
according  to  the  duration  of  the  action.  After  24  hours  the 
article  treated  shows  a  beautiful  bronze,  but  when  the  mix- 
ture is  allowed  to  act  for  a  greater  length  of  time  the  tone 
is  changed  and  several  different  shades  of  great  beauty  are 
obtained.  After  rinsing,  dry  in  hot  saw-dust  and  lacquer  with 
colorless  spirit  lacquer. 

Copper  is  colored  blue-black  by  dipping  the  object  in  a  hot 
solution  of  \\y±  drachms  of  liver  of  sulphur  in  I  quart  of 
water,  moving  it  constantly.  Bhie-gray  shades  are  obtained 
with  more  dilute  solutions.  It  is  difficult  to  give  definite  di- 
rections as  to  the  length  of  time  the  solution  should  be  allowed 
to  act,  since  this  depends  on  its  temperature  and  concentra- 
tion. With  some  experience  the  correct  treatment,  however, 
will  soon  be  learned. 

The  so-called  cuivre  fume  is  produced  by  coloring  the 
copper  or  coppered  objects  blue-black  with  solution  of  liver  of 
sulphur,  then  rinsing,  and  finally  scratch-brushing  them, 
whereby  the  shade  becomes  somewhat  lighter.  From  raised 
portions  which  are  not  to  be  dark,  but  are  to  show  the  color  of 
copper,  the  coloration  is  removed  by  polishing  upon  a  felt 
wheel  or  bob. 

Black  color  upon  copper  is  produced  by  a  heated  pickle  of 
2  parts  of  arsenious  acid,  4  of  concentrated  muriatic  acid,  I  of 
sulphuric  acid  of  66°  Be.,  and  24  of  water. 

Dead-black  on  copper. — Brush  the  object  over  with  a  solution 
of  i  part  of  platinum  chloride  in  5  of  water,  or  dip  it  in  the 


406  ELECTRO-DEPOSITION    OF   METALS. 

solution.  A  similar  result  4s  obtained  by  dipping  the  copper 
object  in  a  solution  of  nitrate  of  copper  or  of  manganese,  and 
drying  over  a  coal  fire.  These  manipulations  are  to  be  repeated 
until  the  formation  of  a  uniform  dead-black. 

The  following  solution  is  recommended  for  obtaining  a  deep 
black  color  on  copper  and  its  alloys:  Copper  nitrate  100  parts, 
water  100  parts.  The  copper  nitrate  is  dissolved  in  the  water, 
and  the  article,  if  large,  is  painted  with  it;  if  small,  it  may  be 
immersed  in  the  solution.  It  is  then  heated  over  a  clear  coal 
fire  and  lightly  rubbed.  The  article  is  next  placed  in  or 
painted  with  a  solution  of  the  following  composition  :  Potassium 
sulphide  10  parts,  water  100,  hydrochloric  acid  5. 

More  uniform  results,  however,  are  obtained  by  using  a 
solution  about  three  times  more  dilute  than  the  above,  viz. : 
Copper  nitrate  100  parts,  water  300.  Small  work  can  be  much 
more  conveniently  treated  by  immersion  in  the  solution,  and 
after  draining  off  or  shaking  off  the  excess  of  the  solution,  to 
heat  the  work  on  a  hot  plate  until  the  copper  salt  is  decom- 
posed into  the  black  copper  oxide.  It  would  be  difficult  to 
heat  large  articles  upon  a  hot  plate,  but  a  closed  muffle  furnace 
should  give  better  results  than  an  open  coal  fire.  In  any  case 
the  heating  process  should  not  be  continued  longer  than  neces- 
sary to  produce  the  change  mentioned  above. 

Imitation  of  genuine  patina. — Repeatedly  brush  the  objects 
with  solution  of  sal  ammoniac  in  vinegar;  the  action  of  the 
solution  being  accelerated  by  the  addition  of  verdigris.  A 
solution  of  9  drachms  of  sal  ammoniac  and  2^  drachms  of 
potassium  binoxalate  in  I  quart  of  vinegar  acts  still  better. 
When  the  first  coating  is  dry,  wash  the  obfect,  and  repeat  the 
manipulations,  drying  and  washing  after  each  application,  until 
a  green  patina  is  formed.  It  is  best  to  bring  the  articles  after 
being  brushed  over  with  the  solution  into  a  hermetically  closed 
box,  upon  the  bottom  of  which  a  few  shallow  dishes  containing 
very  dilute  sulphuric  or  acetic  acid  and  a  few  pieces  of  marble 
are  placed.  Carbonic  acid  being  thereby  evolved  and  the  air 
in  the  box  being  kept  sufficiently  moist  by  the  evaporation  of 


COLORING,  PATINIZING,  OXIDIZING,  LACQUERING.         407 

water,  the  conditions  required  for  the  formation  of  genuine 
patina  are  thus  fulfilled.  If  the  patina  is  to  show  a  more  bluish 
tone,  brush  the  object  with  a  solution  of  4^  ozs.  of  ammonium 
carbonate  and  I  J^  ozs.  of  sal  ammoniac  in  I  quart  of  water,  to 
which  a  small  quantity  of  gum  tragacanth  may  be  added. 

To  produce  a  steel-gray  color  upon  copper  immerse  the  clean 
and  pickled  objects  in  a  heated  solution  of  chloride  of  antimony 
in  hydrochloric  acid.  By  using  a  strong  electric  current  the 
objects  may  alsp  be  coated  with  a  steel-gray  deposit  of  arsenic 
in  a  heated  arsenic  bath. 

For  coloring  copper  dark  steel-gray,  a  pickle  consisting  of  I 
quart  of  hydrochloric  acid,  0.125  quart  of  nitric  acid,  \y2  ozs. 
of  arsenious  acid,  and  a  like  quantity  of  iron  filings  is  recom- 
mended. 

Various  colors  upon  massive  copper. — First  draw  the  object 
through  a  pickle  composed  of  sulphuric  acid  60  parts,  hydro- 
chloric acid  24.5,  and  lampblack  15.5;  or  of  nitric  acid  IOO 
parts,  hydrochloric  acid  i  j£,  and  lampblack  y±.  Then  dissolve 
in  a  quart  of  water  ^/^  ozs.  of  sodium  hyposulphite,  and  in 
another  quart  of  water  14^  drachms  of  blue  vitriol,  5^£ 
drachms  of  crystallized  verdigris,  and  7^  grains  of  sodium 
arsenate.  Mix  equal  volumes  of  the  two  solutions,  but  no 
more  than  is  actually  necessary  for  the  work  in  hand,  and  heat 
to  between  167°  and  176°  F.  By  dipping  articles  of  copper, 
brass,  or  nickel  in  the  hot  solution  they  become  immediately 
colored  with  the  colors  mentioned  below,  one  color  passing 
within  a  few  seconds  into  the  other,  and  for  this  reason  the 
effect  must  be  constantly  controlled  by  frequently  taking  the 
objects  from  the  bath.  The  colors  successively  formed  are  as 
follows : 

Upon  copper  :  Upon  brass  :  Upon  nickel : 

Orange,                            Golden-yellow,  Yellow, 

Terra-cotta,                      Lemon  color,  Blue, 

Red  (pale),  *     Orange,  Iridescent. 
Blood-red,                         Terra-cotta, 
Iridescent.                         Olive-green. 


408  ELECTRO-DEPOSITION    OF   METALS. 

Some  of  these  colors  not  being  very  durable,  have  to  be  pro- 
tected by  a  eoat  of  lacquer  or  paraffine.  It  is  further  necessary 
to  diligently  move  the  objects,  so  that  all  portions  acquire  the 
same  color.  The  bath  decomposes  rapidly,  and  hence  only 
sufficient  for  2  or  3  hours'  use  should  be  mixed  at  one  time. 

2.  Coloring  of  brass  and  bronzes. — Most  of  the  directions 
given  for  coloring  copper  are  also  available  for  brass  and 
bronzes,  especially  those  for  the  production  of  the  green  patina, 
and  the  oxidized  tones  by  a  mixture  of  ferric  oxide  and  black- 
lead. 

Many  colorations  on  brass,  however,  are  effected  only  with 
difficulty,  and  are  partially  or  entirely  unsuccessful,  as,  for  in- 
stance, coloring  black  with  liver  of  sulphur.  As  a  pickle  for 
the  production  of  a 

Lustrous  black  on  brass,  the  following  solution  may  be  used  : 
Dissolve  freshly  precipitated  carbonate  of  copper,  while  still 
moist,  in  strong  liquid  ammonia,  using  sufficient  of  the  copper 
salt  so  that  a  small  excess  remains  undissolved,  or,  in  other 
words,  that  the  ammonia  is  saturated  with  copper.  The  car- 
bonate of  copper  is  prepared  by  mixing  hot  solutions  of  equal 
parts  of  blue  vitriol  and  of  soda,  filtering  off",  and  washing  the 
precipitate. 

Dilute  the  solution  of  the  copper  salt  in  ammonia  with  one- 
fourth  its  volume  of  water,  add  31  to  46  grains  of  black-lead, 
and  heat  to  between  Q5°  and  104°  F.  Place  the  clean  and 
pickled  objects  in  this  pickle  for  a  few  minutes,  until  they 
show  a  full  black  shade,  then  rinse  in  water,  dip  in  hot  water 
and  dry  in  sawdust.  The  solution  soon  spoils,  and  hence  no 
more  than  required  for  immediate  use  should  be  prepared. 

Another  method  of  coloring  brass  black  has  been  given 
under  "  Deposition  of  Arsenic,"  p.  346. 

Urquhart  states  that  clean  brass  and  copper  may  be  covered 
with  a  firmly  adherent  black  coating  by  placing  them  very 
near  to  the  flames  of  burning  straw.  .  It  will  not  rub  off",  and 
may  be  polished  with  a  soft  cloth. 

S'teel-gray  on  brass  is  obtained  by  the  use  of  a  mixture  of  I 


COLORING,  PATINIZING,  OXIDIZING,  LACQUERING.         409 

lb.  of  strong  hydrochloric  acid  with  I  pint  of  water,  to  which 
are  added  5*^  ozs.  of  iron  filings  and  a  like  quantity  of  pul- 
verized antimonic  sulphide. 

Hydrochloric  acid  compounded  with  arsenious  acid  is  also 
recommended  for  this  purpose.  The  mixture  is  brought  into 
a  lead  vessel,  and  the  objects  dipped  in  it  should  come  in 
contact  with  the  lead  of  the  vessel,  or  be  wrapped  around  with 
a  strip  of  lead. 

A  gray  color  with  a  bluish  tint  upon  brass  is  produced  with 
solution  of  antimonious  chloride  (butter  of  antimony),  while  a 
pure  steel-gray  color  is  obtained  with  a  hot  solution  of  arsenious 
chloride  with  a  little  water. 

A  pale  gold  color  on  brass  is  obtained  in  the  following  bath  : 
Dissolve  in  90  parts  by  weight  of  water,  3.6  parts  by  weight  of 
caustic  soda  and  the  same  quantity  of  milk  sugar.  Boil  the 
solution  y±  hour.  Then  add  a  solution  of  copper  vitriol  3.6 
parts  by  weight  in  10  of  hot  water  and  use  the  bath  at  a  tem- 
perature of  176°  F. 

Straw  color,  to  brown,  through  golden  yellow,  and  tombac 
color  on  brass  may  be  obtained  with  solution  of  carbonate  of 
copper  in  caustic  soda  lye.  Dissolve  5^5  ozs.  of  caustic  soda 
in  I  quart  of  water,  and  add  I  ^  ozs.  of  carbonate  of  copper. 
By  using  the  solution  cold,  a  dark  golden-yellow  is  first  formed, 
which  finally  passes  through  pale  brown  into  dark  brown  with  a 
green  lustre ;  with  the  hot  solution  the  coloration  is  more 
rapidly  effected. 

A  color  resembling  gold  or  brass  is,  according  to  Dr.  Kayser, 
obtained  as  follows:  Dissolve  8^  drachms  of  sodium  hypo- 
sulphite in  17  drachms  of  water,  and  add  5.64  drachms  of 
solution  of  antimonious  chloride.  Heat  the  mixture  to  boiling 
for  some  time,  then  filter  off  the  red  precipitate  formed,  and 
after  washing  it  several  times  upon  the  filter  with  vinegar,  sus- 
pend it  in  2  or  3  quarts  of  hot  water ;  then  heat  and  add  con- 
centrated soda  lye  until  solution  is  complete.  In  this  hot 
solution  dip  the  clean  and  pickled  brass  objects,  removing  them 
frequently  to  see  whether  they  have  acquired  the  desired  colo- 


410  ELECTRO-DEPOSITION    OF   METALS. 

ration.  The  articles  become  gray  by  regaining  too  long  in  the 
bath. 

Broivn  color,  called  bronze  Ba'rbcdienne,  on  brass. — This  beau- 
tiful color  may  be  produced  as  follows :  Dissolve  by  vigorous 
shaking  in  a  bottle,  freshly  prepared  arsenious  sulphide  in  spirit 
of  sal  ammoniac,  and  compound  the  solution  with  antimonious 
sulphide  until  a  slight  permanent  turbidity  shows  itself,  and  the 
fluid  has  acquired  a  deep  yellow  color.  Heat  the  solution  to 
95°  F.,  and  suspend  the  brass  objects  in  it.  They  become  at 
first  golden-yellow  and  then  brown,  but  as  they  come  from  the 
bath  with  a  dark  dirty  tone,  they  have  to  be  several  times 
scratch-brushed  to  bring  out  the  color.  If,  after  using  it  several 
times,  the  solution  fails  to  work  satisfactorily,  add  some  anti- 
monious sulphide.  The  solution  decomposes  rapidly,  and 
should  be  prepared  fresh  every  time  it  is  to  be  used. 

By  this  method  only  massive  brass  objects  can  be  colored 
brown ;  to  brassed  zinc  and  iron  the  solution  imparts  brown- 
black  tones,  which,  however,  are  also  quite  beautiful. 

Upon  massive  brass,  as  well  as  upon  brassed  zinc  and  iron 
objects,  bronze  Barbedienne  may  be  produced  as  follows : 
Mix  3  parts  of  red  sulphide  of  antimony  (stibium  sulfuratum 
aurantianum}  with  I  part  of  finely  pulverized  bloodstone,  and 
triturate  the  mixture  with  ammonium  sulphide  to  a  not  too 
thickly-fluid  pigment.  Apply  this  pigment  to  the  objects 
with  a  brush,  and,  after  allowing  it  to  dry  in  a  drying  chamber, 
remove  the  powder  by  brushing  with  a  soft  brush. 

In  Paris  bronze  articles  are  colored  dead-yellow  or  clay- 
yellow  to  dark  brown  by  first  brushing  the  pickled  and  thor- 
oughly rinsed  objects  with  dilute  antimony  bisulphide,  and, 
after  drying,  removing  the  coating  of  separated  sulphur  by 
brushing.  Dilute  solution  of  sulphide  of  arsenic  in  ammonia 
is  then  applied,  the  result  being  a  color  resembling  mosaic 
gold.  The  more  frequently  the  arsenic  solution  is  applied, 
the  browner  the  color  becomes.  By  substituting  for  the 
arsenic  solution  one  of  sulphide  of  antimony  in  ammonia  or 
ammonium  sulphide,  colorations  of  a  more  reddish  tone  are 
obtained. 


COLORING,  PATINIZING,  OXIDIZING,  LACQUERING.         41! 

Smoke-bronze. — Bronzing  with  smoke  is  sometimes  resorted 
to  in  order  to  give  the  metal  an  ancient  appearance.  This  is 
effected  by  exposing  the  work  to  the  smoke  of  a  fire  for  some 
days,  when  it  receives  a  firm  coating  of  a  dark  color.  The 
articles  are  generally  suspended  over  the  smoky  fire  of  a 
furnace  by  means  of  brass  wire.  When  'the  furnace  is  suffi- 
ciently heated  the  smoke  is  maintained  by  burning  hay  and 
other  substances  which  produce  copious  smoke  with  the  coal. 
When  the  right  tint  is  attained  the  articles  are  removed  from 
the  furnace  and  allowed  to  cool  without  touching  them  with 
the  hands.  The  hotter  the  articles  have  been  made  the 
darker  will  be  the  color.  If  the  articles  which  have  been 
smoked  have  been  previously  coated  with  a  green  bronze, 
then  it  is  well  to  finish  with  a  waxed  brush. 

Violet-  and  corn-flower  blue  upon  brass  may  be  produced  as 
follows:  Dissolve  in  I  quart  of  water  4^  ozs.  of  sodium  hypo- 
sulphite, and  in  another  quart  of  water  I  oz.  3^  drachms  of 
crystallized  sugar  of  lead,  and  mix  the  solutions.  Heat  the 
mixture  to  176°  F.,  and  then  immerse  the  articles,  moving  them 
constantly.  First  a  gold-yellow  coloration  appears,  which, 
however,  soon  passes  into  violet  and  blue,  and  if  the  bath  be 
allowed  to  act  further,  into  green.  The  action  is  based  upon 
the  fact  that  in  an  excess  of  hyposulphite  of  soda,  solution  of 
hyposulphite  of  lead  is  formed,  which  decomposes  slowly  and 
separates  sulphide  of  lead,  which  precipitates  upon  the  brass 
objects  and  produces  the  various  lustrous  colors. 

Similar  lustrous  colors  are  obtained  by  dissolving  2.11  ozs. 
of  pulverized  tartar  in  I  quart  of  water,  and  I  oz.  of  chloride  of 
tin  in  y2  pint  of  water,  mixing  the  solution,  heating,  and  pour- 
ing the  clear  mixture  into  a  solution  of  6.34  ozs.  of  sodium 
hyposulphite  in  I  pint  of  water.  Heat  this  mixture  to  176°  F., 
and  immerse  the  pickled  brass  objects. 

Ebermayer*  s  experiments  in  coloring  brass. — In  the  following 
the  results  of  Ebermayer's  experiments  are  given,  In  testing 
the  directions,  the  same  results  as  those  claimed  by  Ebermayer 
were  not  always  obtained  ;  and  variations  are  given  in  paren- 
theses. 


412  ELECTRO-DEPOSITION    OF   METALS. 

I.  Blue  vitriol  8  parts  by  weight,  crystallized  sal  ammoniac 
2,  water  100,  give  by  boiling  a  greenish  color.      (The  color  is 
olive-green,   and    useful    for   many    purposes.     The    coloration 
however    succeeds    only    upon    massive    brass,  but    not    upon 
brassed  zinc.) 

II.  Potassium  chlorate    10  parts  by  weight,  blue  vitriol  10, 
water  1000,  given  by  boiling  a  brown-orange  to  cinnamon-brown 
color.      (Only  a  yellow-orange  color  could  be  obtained.) 

III.  By  dissolving  8  parts  by  weight  of  blue  vitriol  in  1000 
of  water,  and  adding  100  of  caustic  soda  until  a  precipitate  is 
formed,  and  boiling  the  objects  in  the  solution,  a  gray-brown 
color  is  obtained,  which  can  be  made  darker  by  the  addition  o* 
colcothar.      (Stains  are  readily  formed.     Brassed  zinc  acquires 
a  pleasant  pale-brown.) 

IV.  With  50  parts  by  weight  of  caustic  soda,  50  of  sulphide 
of  antimony,  and  500  of  water,  a  pale  fig-brown  color  is  pro- 
duced.     (Fig-brown  could  not  be  obtained,  the  shade  being 
rather  dark  olive-green.) 

V.  By  boiling  400  parts  by  weight  of  water,  25  of  sulphide 
of  antimony,  and  60  of  calcined  soda,  and  filtering  the  hot  solu- 
tion, mineral  kermes  is  precipitated.     By  taking  of  this  5  parts 
by  weight  and  heating  with  5  of  tartar,  400  of  water,  and  10  of 
sodium  hyposulphite,  a  beautiful  steel-gray  is  obtained.      (The 
result  is  tolerably  sure  and  good.) 

VI.  Water    400    parts    by    weight,   potassium    chlorate    20, 
nickel  sulphide   10,  give  after  boiling  for  some  time  a  brown 
color,  which,  however,  is   not   formed    if   the   sheet   has   been 
pickled.      (The  brown  color  obtained  is  not  very  pronounced.) 

VII.  Water  250  parts  by  weight,  potassium  chlorate  5,  car- 
bonate of  nickel  2,  and  sulphate  of  ammonium  and  nickel   5, 
give  after  boiling  for  some  time  a  brown-yellow  color,  playing 
into  a  magnificent  red.      (The  results  obtained  were  only  in- 
different.) 

VIII.  Water  250  parts  by  weight,  potassium  chlorate  5,  and 
sulphate  of   nickel  and   ammonium    10,  give  a  beautiful  dark 
brown.      (Upon  massive  brass  a  good  dark-brown  is  obtained. 
The  formula,  however,  is  not  available  for  brassed  zinc.) 


COLORING,  PATINIZING,  OXIDIZING,  LACQUERING.         413 

3.  Coloring  zinc. — The  results  obtained  by  coloring  zinc 
directly  according  to  existing  directions  cannot  be  relied  on, 
and  it  is,  therefore,  recommended  to  first  copper  the  zinc  and 
then  color  the  coppering.  Experiments  in  coloring  zinc  black 
with  alcoholic  solution  of  chloride  of  antimony  according  to 
Dullas's  process  gave  no  useful  results.  Puscher's  method  is 
better ;  according  to  it  the  objects  are  dipped  in  a  boiling 
solution  of  5.64  ozs.  of  pure  green  vitriol  and  3.17  ozs.  of  sal 
ammoniac  in  2^/2  quarts  of  water.  The  loose  black  precipitate 
deposited  upon  the  objects  is  removed  by  brushing,  the  object 
again  dipped  in  the  hot  solution  and  then  held  over  a  coal  fire 
until  the  sal  ammoniac  evaporates.  By  repeating  the  opera- 
tion three  or  four  times  a  firmly  adhering  black  coating  is 
formed.  To  color  zinc  black  with  nitrate  of  manganese,  as 
proposed  by  Neumann,  is  a  tedious  operation,  it  requiring  to 
be  repeated  seven  or  eight  times.  It  is  done  by  dipping  the 
object  in  a  solution  of  nitrate  of  manganese  and  heating  over  a 
coal  fire,  the  manipulations  being  repeated  until  a  uniform 
dead-black  is  obtained. 

By  suspending  zinc  in  a  nickel  bath  slightly  acidulated  with 
sulphuric  acid,  a  firmly  adhering  blue-black  coating  is,  after 
some  time,  formed  without  the  use  of  a  current.  This  coating 
is  useful  for  many  purposes.  A  similar  result  is  attained  by 
immersing  the  zinc  objects  in  a  solution  of  2.11  ozs.  of  the 
double  sulphate  of  nickel  and  ammonium  and  a  like  quantity 
of  sal  ammoniac  in  I  quart  of  water.  The  articles  become 
first  dark  yellow,  then,  successively,  brown,  purple-violet,  and 
indigo-blue,  and  stand  slight  scratch-brushing  and  polishing. 

A  gray  coating  on  zinc  is  obtained  by  a  deposit  of  arsenic  in 
a  heated  bath  composed  of  2.82  ozs.  of  arsenious  acid,  8.46 
drachms  of  sodium  pyrophosphate,  and  I  ^  drachms  of  98  per 
cent,  potassium  cyanide  and  I  quart  of  water.  A  strong  cur- 
rent should  be  used  so  that  a  vigorous  evolution  of  hydrogen 
is  perceptible.  Platinum  sheets  or  carbon  plates  are  used  as 
anodes. 

A  sort  of  bronzing  on  zinc  is  obtained  by  rubbing  it  with  a 


414  ELECTRO-DEPOSITION    OF   METALS. 

paste  of  pipe-clay  to  which  has  been  added  a  solution  of  I  part 
by  weight  of  crystallized  verdigris,  I  of  tartar,  and  2  of  crystal- 
lized soda. 

Kletzinski  states  that  a  solution  of  molybdic  acid,  or  ammo- 
nium molybdate,  in  nitric  acid,  made  very  dilute,  furnishes  a 
good  liquid  for  producing  a  brown  patina  on  cast  zinc.  The 
object  assumes  iridescent  colors  on  immersion  which  he  con- 
siders to  be  due  to  molybdenum  oxide  The  following  pro- 
portions were  tried  with  the  following  results :  Ammonium 
molybdate  1,550  grains,  ammonia  2,325  grains,  water  I  pint. 

Zinc  acquired  a  beautiful  iridescent  appearance  after  a  few 
moments'  immersion  in  the  solution.  On  continuing  the  pro- 
cess, the  iridescent  colors  were  succeeded  by  a  light  yellowish- 
brown  color,  and  this,  on  warming  the  solution,  was  followed 
by  a  slaty-black,  which  was  more  opaque  than  any  of  the  pre- 
ceding colors. 

Brass  and  tin  are  unaffected  when  immersed  alone,  but  tin 
when  placed  in  contact  with  zinc  assumes  a  beautiful  dark  violet 
color,  which  is  firmly  adherent  to  the  metal.  Iron  in  contact 
with  tin  is  simply  stained. 

Red-brown  color  on  zinc. — Rub  with  solution  of  chloride  of 
copper  in  liquid  ammonia. 

Yellow-brown  shades  on  zinc. — Rub  with  solution  of  chloride 
of  copper  in  vinegar. 

4.  Coloring  of  iron. — The  browning  of  gun-barrels  is  effected 
by  the  application  of  a  mixture  of  equal  parts  of  butter  of  anti- 
mony and  olive  oil.  Allow  the  mixture  to  act  for  12  to  14 
hours,  then  remove  the  excess  with  a  woollen  rag  and  repeat 
the  application.  When  the  second  application  has  acted  for  12 
to  24  hours,  the  iron  or  steel  will  be  coated  with  a  bronze- 
colored  layer  of  ferric  oxide  with  antimony,  which  resists  the 
action  of  the  air  and  may  be  made  lustrous  by  brushing  with  a 
waxed  brush. 

A  lustrous  black  on  iron  is  obtained  by  the  application  of 
solution  of  sulphur  in  spirits  of  turpentine  prepared  by  boiling 
upon  the  water  bath.  After  the  evaporation  of  the  spirits  of 


COLORING,  PATINIZING,  OXIDIZING,  LACQUERING.         415 

turpentine  a  thin  layer  of  sulphur  remains  upon  the  iron,  which, 
on  heating  the  object,  immediately  combines  with  the  metal. 

By  another  method  the  cleansed  and  pickled  iron  objects  are 
coated,  when  dry,  with  linseed  oil,  and  heated  to  a  dark  red. 
If  pickling  is  omitted,  the  coating  with  linseed  oil  and  heating 
may  have  to  be  repeated  two  or  three  times. 

According  to  Meritens  a  bright  black  color  can  be  obtained 
on  iron  by  making  it  the  anode  in  distilled  water,  kept  at  158° 
F.,  and  using  an  iron  plate  as  a  cathode.  The  method  was 
tested  as  follows :  A  piece  of  bright  sheet  pen-steel  was  placed 
in  distilled  water  and  made  the  anode  by  connecting  with  the 
positive  pole  of  a  plating  dynamc,  and  a  similar  sheet  was  con- 
nected with  the  negative  pole  to  form  the  cathode.  An  electro- 
motive force  of  8  volts  was  employed.  After  some  time  a  dark 
stain  was  produced,  but  wanting  in  uniformity.  The  experi- 
ment was  repeated  with  larger  plates,  when  a  good  blue-black 
color  was  obtained  on  the  anode  in  half  an  hour.  On  drying 
out  in  sawdust  the  color  appeared  less  dense,  and  inclined  to  a 
dark  straw  tint.  The  back  of  the  plate  was  also  colored,  but 
not  regularly.  The  face  of  the  cathode  "was  discolored  with  a 
grayish  stain  on  the  side  opposite  to  the  anode,  but  on  the 
other  side  the  appearance  was  almost  identical  with  the  back  of 
the  anode.  The  water  became  of  a  yellowish  color. 

Fresh  distilled  water  was  then  boiled  for  a  long  time  so  as 
to  expel  all  trace  of  the  oxygen  absorbed  from  the  atmosphere, 
and  the  experiment  repeated  as  in  the  former  cases.  No  per- 
ceptible change  took  place  after  the  connection  had  been  made 
with  the  dynamo  for  a  quarter  of  an  hour.  After  the  interval 
of  one  hour  a  slight  darkening  occurred,  but  the  effect  was 
much  less  than  that  produced  in  five  minutes  in  aerated  water. 

The  action  of  the  liquid  in  coloring  the  steel  is  evidently  one 
of  oxidation,  due  to  the  dissolved  oxygen,  which  becomes 
more  chemically  active  under  the  influence  of  the  electric  con- 
dition, and  gradually  unites  with  the  iron. 

The  dead  black  coating  on  clock  cases  of  iron  and  steel  is 
not  produced  by  the  galvanic  process. 


416  ELECTRO-DEPOSITION    OF   METALS. 

According  to  Bottger  a  durable  blue  on  iron  and  steel  may 
be  obtained  by  dipping  the  article  in  a  ^  per  cent,  solution  of 
red  prussiate  of  potash  mixed  with  an  equal  volume  of  a  ^ 
per  cent,  ferric  chloride  solution. 

A  brown-black  coating  with  bronze  lustre  on  iron  is  obtained 
by  heating  the  bright  iron  objects  and  brushing  them  over 
with  concentrated  solution  of  potassium  bichromate.  When 
dry,  heat  them  over  a  charcoal  fire  and  wash  until  the  water 
running  off  shows  no  longer  a  yellow  color.  Repeat  the 
operation  twice  or  three  times.  A  similar  coating  is  obtained 
by  heating  the  iron  objects  with  a  solution  of  10  parts  by 
weight  of  green  vitriol  and  I  part  of  sal  ammoniac  in  water. 

To  give  iron  a  silvery  appearance  with  high  lustre. — Scour 
the  polished  and  pickled  iron  objects  with  a  solution  prepared 
as  follows :  Heat  moderately  I  y2  ozs.  of  chloride  of  antimony, 
0.35  oz.  of  pulverized  arsenious  acid,  2.82  ozs.  of  elutriated 
bloodstone  with  I  quart  of  90  per  cent,  alcohol  upon  a  water 
bath  for  half  an  hour.  Partial  solution  takes  place.  Dip  into 
this  fluid  a  tuft  of  cotton  and  go  over  the  iron  portions,  using 
slight  pressure.  A  thin  film  of  arsenic  and  antimony  is  thereby 
deposited,  which  is  the  more  lustrous  the  more  carefully  the 
iron  has  been  previously  polished. 

5.  Coloring  of  tin. — A  bronze-like  patina  on  tin  may  be  ob- 
tained by  brushing  the  object  over  with  a  solution  of  I  ^  ozs. 
of  blue  vitriol  and  a  like  quantity  of  green  vitriol  in  I  quart  of 
water,  and  moistening  the  object  when  dry  with  a  solution  of 
3^£  ozs.  of  verdigris  in  10^  ozs.  of  vinegar.  When  dry,  polish 
the  object  with  a  soft  waxed  brush  and  some  ferric  oxide.  The 
coating  thus  obtained  being  not  especially  durable,  must  be 
protected  by  a  coating  of  lacquer. 

Durable  and  very  warm  sepia-brown  tone  upon  tin  and  its 
alloys. — Brush  the  object  over  with  a  solution  of  I  part  of  plat- 
inum chloride  in  10  of  water,  allow  the  coating  to  dry,  then 
rinse  in  water,  and,  after  again  drying,  brush  with  a  soft  brush 
until  the  desired  brown  lustre  appears. 

A  dark  coloration  is  also  obtained  with  ferric  chloride 
solution. 


COLORING,  PATINIZING,  OXIDIZING,  LACQUERING.         417 
6.   Coloring  of  silver. — See  "  Silvering,"  p.  282. 

Lacquering. 

In  the  electro-plating  industry  recourse  is  frequently  had  to 
lacquering  in  order  to  make  the  deposits  more  resistant  against 
atmospheric  influences,  or  to  protect  artificially  prepared  colors, 
patinas,  etc.  Thin,  colorless  shellac  solution,  which  does  not 
affect  the  color  of  the  deposit  or  of  the  patinizing,  is,  as  a  rule, 
employed,  while  in  some  cases  colored  lacquers  are  used  to 
heighten  the  tone  of  the  deposit,  as,  for  instance,  gold  lacquer 
for  brass. 

The  lacquer  is  applied  by  means  of  a  fine  flat  fitch-brush, 
the  object  having  previously  been  heated  hand-warm.  After 
lacquering,  the  object  is  dried  in  an  oven  at  a  temperature  of 
between  140°  and  158°  F.,  whereby  small  irregularities  are  ad- 
justed, and  the  layer  of  lacquer  becomes  transparent,  clear,  and 
lustrous. 

Cellulose  lacquers  and  varnishes. — Under  the  name  of  zapon 
a  dip-lacquer  has  been  introduced  in  commerce.  It  represents 
a  clear,  almost  colorless  fluid  of  the  consistency  of  collodion, 
and  smells  something  like  fruit  ether.  According  to  G.  Buch- 
ner,  it  consists  essentially  of  a  solution  of  cellulose  in  a  mixture 
of  amyl  acetate  and  acetone.  Of  the  last  two  bodies,  the 
"thinning  fluid,"  which  accompanies  the  preparation,  also  con- 
sists. This  lacquer  can  be  highly  recommended,  its  superiority 
being  due  to  the  favorable  properties  of  the  cellulose.  The 
transparent,  colorless  coat  obtained  with  zapon  can  be  bent  with 
the  metallic  sheet,  to  which  it  has  been  applied,  without  crack- 
ing. It  is  so  hard  that  it  can  scarcely  be  scratched  with  the 
finger-nail,  shows  no  trace  of  stickiness,  and  it  is  perfectly 
homogeneous  even  on  the  edges.  This  favorable  behavior  is 
very  likely  due  to  the  slow  evaporation  of  the  solvent,  and  the 
fact  that  the  lacquer  quickly  forms  a  thickish,  tenacious  layer, 
which,  though  moved  with  difficulty,  is  not  entirely  immobile. 
Another  advantage  of  zapon — especially  as  regards  metallic 
objects — is  that  the  coating,  in  consequence  of  its  physical  con- 
27 


41 8  ELECTRO-DEPOSITION    OF   METALS. 

stitution,  preserves  the  character  of  the  basis.  In  accordance 
with  the  nature  of  cellulose,  the  coating  is  not  sensibly  affected 
by  ordinary  differences  in  temperature,  and  does  not  become 
dull  and  non-transparent,  as  is  the  case  with  resins,  in  conse- 
quence of  the  loss  of  molecular  coherence.  It  can  be  washed 
with  soap  and  water,  and  protects  metals  coated  with  it  from 
the  action  of  the  atmosphere.  Zapon  may  also  be  colored,  but, 
of  course,  only  with  coloring  substances — mostly  aniline  colors 
— which  are  soluble  in  the  solvent  used  for  the  cellulose. 

A  similar  preparation  is  known  as  kristaline.  It  is  a  hard, 
transparent  enamel,  which  can  be  applied  as  a  lacquer  in  all 
kinds  of  metal-work  without  affecting  the  most  delicate  finish. 
It  is  applied  by  dipping,  is  invisible,  and  leaves  no  mark  in 
drying. 

Kristaline  has  now  been  in  use  for  about  ten  years,  and  can 
be  relied  upon  to  protect  all  metal-work  from  acids  and  alkalies, 
also  coal-gas,  alcohol,  benzine,  oil,  water,  fly-specks,  etc.  It  is 
especially  designed  to  prevent  the  highest  class  of  metal-work 
from  tarnishing  and  to  preserve  the  delicate  shades  of  color 
produced  by  electricity  and  artificial  oxidation. 

A  lacquer  similar  to  zapon  or  kristaline  may  be  prepared  by 
substituting  soluble  pyroxylin  for  cellulose,  the  process  being 
as  follows  :  Bring  collodion-cotton,  i.  e.,  soluble  pyroxylin,  such 
as  is  used  by  photographers,  into  a  box  which  can  be  hermetic- 
ally closed,  and  place  upon  the  bottom  of  the  box  a  dish  with 
sulphuric  acid.  The  purpose  of  this  is  to  dry  the  collodion- 
cotton,  which  requires  from  36  to  48  hours.  The  collodion- 
cotton  is  then  brought  into  a  large  bottle,  and  three  to  four 
times  its  quantity  by  weight  of  very  strong  alcohol  poured  over 
it.  In  a  few  days  the  greater  portion  of  it  is  dissolved,  when 
the  clear  solution  is  poured  into  another  bottle.  Add  to  the 
clear  solution  more  collodion-cotton,  about  25  to  30  per  cent, 
of  the  weight  of  the  quantity  originally  used,  and  the  resulting 
product  forms  an  excellent  cellulose  lacquer,  which  rapidly 
hardens  to  a  perfectly  transparent  and  very  glossy  coating. 
For  diluting  cellulose  lacquers  it  is  best  to  use  wood  spirit.  To 


COLORING,  PATINIZING,  OXIDIZING,  LACQUERING.         419 

color  them,  dissolve  an  aniline  color  in  strong  spirits  of  wine, 
add  a  corresponding  quantity  of  the  solution  to  the  lacquer, 
and  shake  vigorously. 

In  conclusion,  a  few  words  may  be  said  in  regard  to  the  pro- 
cesses by  which  those  magnificent  effects  are  obtained  which 
imitate  so  completely  the  appearance,  freshness,  and  rich  tones 
of  real  gilding.  In  general,  gold  varnish  is  applied  only  upon 
copper  and  its  more  or  less  yellow  alloys. 

Gold  varnishers  operate  as  follows :  After  the  objects  have 
been  perfectly  cleansed,  scratch-brushed,  and  burnished,  if 
necessary,  they  are  completely  dried  in  hot  sawdust  and  wiped 
clean  with  a  fine  cloth.  A  light  coat  of  varnish  is  then  applied 
with  a  fitch-pencil,  and  all  excess  of  varnish  removed  or  leveled 
with  another  flat  brush  of  badger-hair  or  bristles.  The  two 
brushes  are  kept  together  in  the  same  hand,  the  varnish  brush 
between  the  thumb  and  first  two  fingers,  while  the  flat  one 
(without  a  handle)  is  held  between  the  other  fingers  and  the 
palm  of  the  hand.  In  this  manner  there  is  no  interval  in  the 
use  of  the  two  brushes.  The  varnish  is  kept  in  a  jelly-pot  or 
other  similar  vessel,  across  the  top  of  which  a  string  has  been 
stretched.  This  string  is  intended  for  removing  by  wiping  the 
excess  of  varnish  taken  up  by  the  brush  or  pencil.  The  varnish 
which  covers  the  burnished  parts  of  the  object  may  be  removed 
with  a  clean  rag  moistened  with  alcohol  and  wrapped  round  the 
finger.  Another  dry  cloth  finishes  the  drying.  Sometimes  the 
burnished  parts  are  also  varnished,  but  the  operation  is  very 
difficult  when  their  surface  is  considerable.  Round-ware,  pol- 
ished or  burnished,  may  be  varnished  in  the  lathe. 

After  the  varnish  has  been  applied  as  uniformly  as  possible, 
the  objects  are  put  in  a  drying  stove  heated  to  between  140° 
and  175°  F.  The  alcohol  or  essential  oils  of  the  varnish  are 
rapidly  volatilized,  while  the  resins  or  gums  melt  and  cover  the 
objects  with  a  glassy  lustre.  The  heat  must  be  sufficient  to 
melt  these  gums,  but  low  enough  to  avoid  burning  them. 
When  the  operation  has  been  well  performed,  the  pieces  pre- 
sent a  beautiful  and  uniform  golden  appearance,  with  no  disfig- 


420  ELECTRO-DEPOSITION    OF    METALS. 

tiring  red  patches,  which  latter  indicate  an  unequal  thickness  of 
varnish. 

Varnishers  have  always  at  their  disposal  four  varnishes  of 
different  shades — red  gold,  orange-yellow  gold,  green  gold,  and 
colorless  varnish  for  mixture.  This  last  is  employed  for  dilut- 
ing the  first  three  and  diminishing  the  depth  of  their  colors. 
Each  of  these  various  varnishes  gives  to  copper  the  gold  color 
peculiar  to  it,  and,  when  mixed,  intermediary  shades.  It  often 
happens  that  the  various  parts  of  a  large  piece  are  different  in 
composition  and  color,  and  the  varnisher  is  obliged  to  impart 
the  same  shade  of  gold  all  over  by  skilful  combinations  of 
varnishes.  He  thus  succeeds  in  giving  the  same  gold  color  to 
half-red  copper  and  to  alloys  of  yellow  and  green  brass. 

But  a  small  quantity  of  varnish  is  poured  into  the  varnish 
pot  at  one  time,  to  prevent  it  from  thickening  by  evaporation, 
and  after  the  operation  the  residue  is  poured  back  into  the 
flask  from  which  it  was  taken  and  kept  well  stoppered.  The 
brushes  and  pencils  must  be  often  washed  in  alcohol,  which 
may  afterwards  be  used  for  diluting  thick  varnishes. 

These  varnishes  are  made  by  dissolving  various  resinous 
substances,  like  sandarac,  benzoin,  dragon's-blood,  elemi, 
gamboge,  etc.,  and  tinctorial  matters,  such  as  saffron,  annotto, 
alkanet,  etc.,  in  a  mixture  of  alcohol  with  essence  of  lavender 
or  of  spikenard.  All  qualities  of  varnish  are  to  be  found,  but 
the  more  expensive  are  often  the  more  economical. 

To  remove  the  varnish  from  an  imperfectly  varnished  object 
or  from  an  old  one,  it  is  immersed  in  alcohol  or  concentrated 
sulphuric  acid,  or,  better  still,  in  a  boiling  solution  of  caustic 
lye.  The  varnishing  is  then  begun  anew. 


HYGIENIC    RULES    FOR  THE   WORKSHOP.  421 

CHAPTER  XVI. 

HYGIENIC    RULES    FOR   THE   WORKSHOP. 

IN  but  few  otherbranches  of  the  industry  has  the  workman 
so  constantly  to  deal  with  powerful  poisons,  as  well  as  other 
substances  and  vapors,  which  are  exceedingly  corrosive  in 
their  action  upon  the  skin  and  the  mucous  membranes,  as  in 
electro-plating.  However,  with  the  necessary  care  and  sobri- 
ety, all  influences  injurious  to  health  may  be  readily  overcome. 

The  necessity  of  frequently  renewing  the  air  in  the  workshop 
by  thorough  ventilation  has  already  been  referred  to  in  Chapter 
IV.,  "  Electro-plating  establishments  in  general."  Workmen 
exclusively  engaged  in  pickling  objects  are  advised  to  neutralize 
the  action  of  the  acid  upon  the"  enamel  of  the  teeth  and  the 
mucous  membrane  of  the  mouth  and  throat  by  frequently  rins- 
ing the  mouth  with  dilute  solution  of  bicarbonate  of  soda. 
Workmen  engaged  in  freeing  the  objects  from  grease  lose,  for 
want  of  cleanliness,  the  skin  on  the  portions  of  the  fingers 
which  come  constantly  in  contact  with  the  lime  and  caustic 
lyes.  This  may  be  overcome  by  frequently  washing  the  hands 
in  clean  water,  and  previous  to  each  intermission  in  the  work 
the  workman  should  after  washing  the  hands  dip  them  in  dilute 
sulphuric  acid,  dry  them,  and  thoroughly  rub  them  with  cos- 
moline  or  a  mixture  of  equal  parts  of  glycerine  and  water. 
The  use  of  rubber  gloves  by  workmen  engaged  in  freeing  the 
objects  from  grease  cannot  be  recommended,  they  being  ex- 
pensive and  subject  to  rapid  destruction.  It  is  better  to  wrap 
a  linen  rag  seven  or  eight  times  around  a  sore  finger,  many 
workmen  using  this  precaution  to  protect  the  skin  from  the 
corrosive  action  of  the  lime. 

It  should  be  a  rule  for  every  workman  employed  in  an 
electro-plating  establishment  not  to  drink  from  vessels  used  in 
electroplating  manipulations ;  for  instance,  porcelain  dishes, 
beer  glasses,  etc.  One  workman  may  this  moment  use  such  a 


422  ELECTRO-DEPOSITION    OF   METALS. 

vessel  to  drink  from  and  without  his  knowledge  another  may 
employ  it  the  next  moment  for  dipping  out  potassium  cyanide 
solution,  and  the  first  using  it  again  as  a  drinking  vessel  may 
incur  sickness  or  even  fatal  poisoning.  The  handling  of  potas- 
sium cyanide  and  its  solutions  requires  constant  care  and  judg- 
ment. Working  with  sore  hands  in  such  solutions  should  be 
avoided  as  much  as  possible ;  but  if  it  has  to  be  done,  and  the 
workman  feels  a  sharp  pain  in  the  sore,  wash  the  latter  quickly 
with  clean  water  and  apply  a  few  drops  of  green  vitriol  solution. 
Many  individuals  are  very  sensitive  to  nickel  solutions,  erup- 
tions, which  are  painful  and  heal  slowly,  breaking  out  upon  the 
arms  and  hands,  while  others  may  for  years  come  in  contact 
with  nickel  baths  without  being  subject  to  such  eruptions.  In 
such  case  prophylaxis  is  also  the  safeguard,  i.  e.,  to  prevent  by 
immediate  thorough  washing  the  formation  of  the  eruption  if 
the  skin  has  been  brought  in  contact  with  nickel  solution,  as, 
for  instance,  in  taking  out  with  the  hand  an  object  fallen  into  a 
nickel  bath. 

Below  will  be  found  some  directions  for  neutralizing,  in  case 
of  internal  poisoning,  the  effects  of  the  poison  either  entirely 
or  at  least  sufficiently  to  retard  its  action  until  professional  aid 
can  be  summoned. 

Poisoning  by  hydrocyanic  (prussic)  acid,  potassium  cyanide, 
or  cyanides. — If  prussic  acid,  or  the  cyanides,  be  concentrated 
or  have  been  absorbed  in  considerable  quantity,  their  action  is 
almost  instantly  fatal,  and  there  is  little  hope  of  saving  the 
victim,  although  everything  possible  should  be  tried.  But  if 
these  substances  have  been  taken  in  very  dilute  condition, 
they  may  not  prove  immediately  fatal,  and  there  is  some  hope 
that  remedial  measures  may  be  successfully  applied. 

In  poisoning  with  these  substances,  water  as  cold  as  possible 
should  be  run  upon  the  head  and  spine  of  the  patient,  and  he 
should  be  made  to  inhale,  carefully  and  moderately,  the  vapor 
of  chlorine  water,  bleaching  powder,  or  Javelle  water  (hypo- 
chlorite  of  soda). 

Should  these  poisons  be  introduced  into  the  stomach,  there 


HYGIENIC    RULES    FOR  THE   WORKSHOP.  423 

should  be  administered  as  soon  as  possible  the  hydrate  of 
sesquioxide  of  iron,  or,  what  is  better,  dilute  solutions  of  the 
acetate,  citrate,  or  tartrate  of  iron.  With  proper  precautions  a 
very  dilute  solution  of  sulphate  of  zinc  may  be  given. 

Poisoning  by  copper-salts. — The  stomach  should  be  quickly 
emptied  by  means  of  an  emetic  or,  in  want  of  this,  the  patient 
should  thrust  his  finger  to  the  back  of  his  throat  and  induce 
vomiting  by  tickling  the  uvula.  After  vomiting  drink  milk, 
white  of  egg,  gum-water,  or  some  mucilaginous  decoction. 

Poisoning  by  lead-salts  requires  the  same  treatment  as 
poisoning  by  copper-salts.  Lemonade  of  sulphuric  acid,  or 
an  alkaline  solution  containing  carbonic  acid,  such  as  Vichy 
water,  or  bicarbonate  of  soda,  is  also  very  serviceable. 

Poisoning  by  arsenic.  —  The  stomach  must  be  quickly 
emptied  by  an  energetic  emetic,  when  freshly  precipitated 
ferric  hydrate  and  calcined  magnesia  may  be  given  as  an  anti- 
dote. Calcined  magnesia  being  generally  on  hand,  mix  it 
with  1 5  to  20  times  the  quantity  of  water  and  give  of  this  mix- 
ture 3  to  6  tablespoonfuls  every  10  to  15  minutes. 

Poisoning  by  alkalies. — Use  weak  acids,  such  as  vinegar, 
lemon-juice,  etc.,  and  in  their  absence  sulphuric,  hydrochloric, 
or  nitric  acid  diluted  to  the  strength  of  lemonade.  After  the 
pain  in  the  stomach  has  diminished,  it  will  be  well  to  administer 
a  few  spoonfuls  of  olive  oil. 

Poisoning  by  mercury -salts. — Mercury  salts,  and  particularly 
the  chloride  (corrosive  sublimate),  form  with  the  white  of  egg 
(albumen)  a  compound  very  insoluble  and  inert.  The  remedy, 
albumen,  is  therefore  indicated.  Sulphur  and  sulphuretted 
water  are  also  serviceable  for  the  purpose. 

Poisoning  by  sulphuretted  hydrogen. — The  patient  should  be 
made  to  inhale  the  vapor  of  chlorine  from  chlorine  water, 
Javelle  water,  or  bleaching-powder.  Energetic  friction,  espec- 
ially at  the  extremities  of  the  limbs,  should  be  employed. 
Large  quantities  of  warm  and  emollient  drinks  should  be  given, 
and  abundance  of  fresh  air. 

Poisoning  by  chlorine ',  sulphurous  acid,  nitrous  and  hyponitric 


424  ELECTRO-DEPOSITION    OF   METALS. 

gases. — Admit  immediately  an  abundance  of  fresh  air,  and  ad- 
minister light  inspirations  of  ammonia.  Give  plenty  of  hot 
drinks  and  excite  friction,  in  order  to  conserve  the  warmth  and 
transpiration  of  the  skin.  Employ  hot  foot-baths  to  remove 
the  blood  from  the  lungs.  Afterwards  maintain  in  the  mouth 
of  the  patient  some  substance  which,  melting  slowly,  will  keep 
the  throat  moist,  such  as  jujube  and  marshmallow  paste, 
molasses  candy,  and  liquorice  paste.  Milk  is  excellent. 


CHAPTER  XVII. 

CHEMICAL   PRODUCTS   AND   VARIOUS   APPARATUS   AND 
INSTRUMENTS   USED    IN   ELECTRO-PLATING. 

A.  CHEMICAL  PRODUCTS. 

BELOW  the  characteristic  properties  of  the  chemical  pro- 
ducts employed  in  the  workshop  will  be  briefly  discussed, 
and  the  reactions  indicated  which  allow  of  their  recognition. 
It  frequently  happens  that  the  labels  become  detached  from  the 
bottles  and  boxes,  thus  rendering  the  determination  of  their 
contents  necessary. 

I.  Acids. 

I.  Sulphuric  acid  (oil  of  vitriol). — Two  varieties  of  this  acid 
are  found  in  commerce,  viz.,  fuming  sulphuric  acid  (disulphuric 
acid),  and  ordinary  sulphuric  acid.  The  first  is  a  thick  oily 
fluid  generally  colored  yellowish  by  organic  substances,  and 
emits  dense  white  vapors  in  the  air.  Its  specific  gravity  is 
1.87  to  1.89.  The  only  purpose  for  which  fuming  sulphuric 
acid  is  used  in  the  electro-plating  art  is  as  a  mixture  with  nitric 
acid,  for  stripping  silvered  objects. 

Ordinary  sulphuric  acid  has  a  specific  gravity  of  1.84. 
Diluted  with  water  it  serves  for  filling  the  Bunsen  elements  and 
as  a  pickle  for  iron;  in  a  concentrated  state  it  is  used  in  the 


CHEMICAL   PRODUCTS.  425 

preparation  of  pickles  and  as  an  addition  to  the  galvanoplastic 
copper  bath.  The  crude  commercial  acid  generally  contains 
arsenic,  hence  care  must  be  had  to  procure  a  pure  article.  In 
diluting  the  acid  with  water,  it  should  in  all  cases  be  added  to 
the  water  in  a  very  gentle  stream  and  with  constant  stirring,  as 
otherwise  a  sudden  generation  of  steam  of  explosive  violence 
might  result,  and  the  dangerous  corrosive  liquid  be  scattered  in 
all  directions.  Concentrated  sulphuric  acid  vigorously  attacks 
all  organic  substances,  and  hence  has  to  be  kept  in  bottles  with 
glass  stoppers,  and  bringing  it  in  contact  with  the  skin  should 
be  carefully  avoided. 

Recognition. — One  part  of  acid  mixed  with  25  parts  of  dis- 
tilled water  gives,  when  compounded  with  a  few  drops  of  bar- 
ium chloride  solution,  a  white  precipitate  of  barium  sulphate. 

2.  Nitric  acid  (aqua  fortis,  spirit  of  nitre). — It  is   found   in 
trade  of  various  degrees  of  strength ;   for  our  purposes  acid  of 
40°  and  30°  Be.,  being  generally  used.     The  acid  is  usually  a 
more  or  less   deep  yellow,   and   frequently  contains  chlorine. 
The   vapors   emitted   by   nitric   acid   are  poisonous   and    of   a 
characteristic  odor,  by  which  the  concentrated  acid  is  readily 
distinguished  from  other  acids.     It  is  used  for  filling  the  Bun- 
sen   elements,  and   for  pickling  in   combination  with  sulphuric 
acid   and    chlorine.     On   coming  in   contact   with   the   skin   it 
produces  yellow  stains. 

Recognition. — By  heating  the  not  too  dilute  acid  with  copper, 
brown-red  vapors  are  evolved.  For  the  determination  of  dilute 
nitric  acid,  add  a  few  drops  of  it  to  green  vitriol  solution,  when 
a  black-brown  coloration  will  be  produced  on  the  point  of  con- 
tact. 

3.  Hydrochloric  acid  (muriatic  acid). — The  pure  acid   is  a 
colorless  fluid  which  emits  abundant  fumes  in  contact  with  the 
air,  and  has  a  pungent  odor  by  which  it  is  readily  distinguished 
from  other  acids.     The  specific  gravity  of  the  strongest  hydro- 
chloric acid  is  1.2;   the  crude  acid  of  commerce  has  a  yellow 
color,  due  to  iron,  and  contains  arsenic.     Dilute  hydrochloric 
acid  is  used  for  pickling  iron  and  zinc. 


426  ELECTRO-DEPOSITION    OF   METALS. 

Recognition. — On  adding  to  the  acid  strongly  diluted  with 
distilled  water  a  few  drops  of  solution  of  nitrate  of  silver  in 
distilled  water,  a  heavy  white  precipitate  is  formed,  which  be- 
comes black  by  exposure  to  the  light. 

4.  Hydrocyanic  acid(prussic  acid). — This  extremely  poison- 
ous  acid  exists   in   nature   only  in   a  state   of   combination  in 
certain  vegetables  and  fruits,  and   especially  in  the  kernels  of 
the   latter,   as,   for   instance,  in   the   peach,  the  berries   of  the 
cherry   laurel,   bitter   almonds,   the   stones   of    the   apricot,   of 
plums,  cherries,  etc.     It  may  be  obtained  anhydrous,  but  in 
this  state  it  is  useless,  and  very  difficult  to  preserve  from  de- 
composition.    Diluted   hydrocyanic   acid   is   colorless,   with    a 
bitter  taste  and  the  characteristic  smell  of  bitter  almonds.     It 
is  employed  in  the  preparation  of  gold  immersing  baths,  and 
for  the  decomposition  of  the  potassa  in  old  silver  baths.     The 
inhalation  of  the  vapors  of  this  acid  may  have  a  fatal  effect,  as 
also  its  coming  in  contact  with  wounds. 

Recognition. — By  its  characteristic  smell  of  bitter  almonds. 
Or  mix  it  with  potash  lye  until  blue  litmus  paper  is  no  longer 
reddened,  then  add  solution  of  green  vitriol  which  has  been 
partially  oxidized  by  standing  in  the  air,  and  acidulate  with 
hydrochloric  acid.  A  precipitate  of  Berlin  blue  is  formed. 

5.  Citric   acid. — Clear    colorless    crystals   of    1.542    specific 
gravity,  which  dissolve  with  great  ease  in  both   hot  and  cold 
water.     It  is  frequently  employed  for  acidulating  nickel  baths, 
and,  combined  with  sodium  citrate,  in  the  preparation  of  plat- 
inum baths. 

Recognition. — Lime-water  compounded  with  aqueous  solution 
of  citric  acid  remains  clear  in  the  cold,  but  on  boiling  deposits 
a  precipitate  of  calcium  citrate.  This  precipitate  is  soluble  in 
ammonium  chloride,  but  on  boiling  is  again  precipitated,  and  is 
then  insoluble  in  sal  ammoniac. 

6.  Boric  acid  (boracic  acid}. — This  acid   is  found  in  com- 
merce in  the  shape  of  scales  with  nacreous  lustre  and  greasy  to 
the  touch ;    when  obtained    from  solutions  by  evaporation,  it 
forms  colorless  prisms.     Its  specific  gravity  is  1.435  ;  it  dissolves 


CHEMICAL    PRODUCTS.  427 

with  difficulty  in  cold  water  (i  part  of  acid  requiring,  at  64.4° 
F.,  28  of  water),  but  is  more  rapidly  soluble  in  boiling  water 
(  i  part  of  acid  requiring  3  of  water  at  212°  F.) .  According  to 
Weston's  proposition,  boric  acid  is  employed  as  an  addition  to 
nickel  baths,  etc. 

Recognition. — By  mixing  solution  of  boric  acid  in  water  with 
some  hydrochloric  acid  and  dipping  turmeric  paper  in  the  solu- 
tion, the  latter  acquires  a  brown  color,  the  color  becoming 
more  intense  on  drying.  Alkalies  impart  to  turmeric  paper  a 
similar  coloration,  which,  however,  disappears  on  immersing 
the  paper  in  dilute  hydrochloric  acid. 

7.  Arsenious  acid  (white  arsenic,  arsenic,  ratsbane}. — It  gen- 
erally occurs  in  the  shape  of  a  white  powder  and   sometimes  in 
vitreous-like  lumps,  resembling  porcelain  ;  for  our  purposes  the 
white  powder  is  almost  exclusively  used.     It  is  slightly  soluble 
in  cold  water,  and   more  readily  in  hot  water  and   hydrochloric 
acid.     Notwithstanding  its  greater  specific  gravity  (3.7)  only  a 
portion  of  the  powder  sinks  to  the  bottom  on  mixing  it  with 
water,  another  portion  being  retained   on  the   surface   by  air 
bubbles  adhering  to  it.     It  is  employed  as  an  addition  to  brass 
baths,  further,  in  the  preparation  of  arsenic  baths,  for  blacking 
copper  alloys,  and  in  certain  silver  whitening  baths. 

Recognition. — When  some  arsenious  acid  is  thrown  upon 
glowing  coals  an  odor  resembling  that  of  garlic  is  perceptible. 
By  mixing  solution  of  arsenious  acid,  prepared  by  boiling  with 
water,  with  a  few  drops  of  ammoniacal  solution  of  nitrate  of 
silver,  a  yellow  precipitate  of  arsenate  of  silver  is  obtained. 
The  ammoniacal  solution  of  nitrate  of  silver  is  prepared  by 
adding  ammonia  to  solution  of  nitrate  of  silver  until  the  pre- 
cipitate at  first  formed  disappears. 

8.  Chromic  acid. — It   forms   crimson- red    needles,  and   also 
occurs  in  commerce  in  the  shape  of  a  red   powder.     It  is  read- 
ily soluble  in  water,  forming  a  red  fluid  which  serves  for  filling 
batteries. 

Recognition. — Chromic  acid  can  scarcely  be  mistaken  for  any 
other  chemical  product  employed  by  the  electro-plater.  A 


428  ELECTRO-DEPOSITION    OF   METALS. 

strongly  diluted  solution  of  it  gives,  after  neutralizing  with 
caustic  alkali  and  adding  a  few  drops  of  nitrate  of  silver  solu- 
tion, a  crimson-red  precipitate  of  chromate  of  silver. 

9.  Hydrofluoric   acid. — A  colorless,  corrosive,  very    mobile 
liquid  of  a  sharp,  pungent  odor.     The   anhydrous  acid  fumes 
strongly  in  the  air  and  attracts  moisture  with  avidity.     Hydro- 
fluoric acid  is  used  for  etching  glass  and  for  pickling  aluminium 
dead  white.     Great  care  must  be  observed  in  working  with  the 
acid,  since  not  only  the  aqueous  solution,  but  also  the  vapors, 
have  an  extremely  corrodent  effect  upon  the  skin  and  respira- 
tory organs. 

Recognition. — By  covering  a  small  platinum  dish  containing 
hydrofluoric  acid  with  a  glass-plate  free  from  grease,  the  latter 
in  half  an  hour  appears  etched. 

II.  Alkalies  and  Alkaline  Earths. 

10.  Potassium  hydrate  {caustic potash}. — It  is  found  in  com- 
merce in  various  degrees  of  purity,  either  in  sticks   or  cakes. 
It  is  very  deliquescent  and  dissolves  readily  in  water  and  alco- 
hol ;   by  absorbing  carbonic  acid  from  the  air  it  rapidly  becomes 
converted  into  the  carbonate  and  thus  loses  its  caustic  proper- 
ties.    It    should,   therefore,   be   stored   in   well  closed   vessels. 
Substances  moistened  with  solution  of  caustic  potash  give  rise 
to   a  peculiar  soapy  sensation  of  the  skin  when  touched.     It 
should  never  be   allowed  to   enter  the   mouth,  as   even   dilute 
solutions   almost  instantaneously  remove  the   lining  of  tender 
skin.     Should  such  an  accident  happen,  the  mouth  should  be 
at  once  several  times  rinsed  with  water  and  then  with  very  di- 
lute acetic  acid.     Pure  caustic  potash  serves  as  an  addition  to 
zinc  baths,  gold  baths,  etc.     For  the  purpose  of  freeing  objects 
from  grease  the  more  impure  commercial  article  is  used. 

11.  Sodium  hydrate  {caustic  soda}. — It  also  occurs  in  com- 
merce  in  various  degrees  of  purity,  either  in   sticks   or  lumps. 
It  is  of  a  highly  caustic   character  resembling  potassium  hy- 
drate (see  above)  in   properties  and  effects.     It   is   employed 
for  freeing  objects  from  grease. 


CHEMICAL    PRODUCTS.  429 

12.  Ammonium  hydrate  (ammonia  or  spirits  of  hartshorn). 
— It  is  simply  water  saturated  with  ammonia  gas.     By  expos- 
ure  ammonia   gas   is   gradually   evolved,   so   that   it   must    be 
stored   in   closely-stoppered  bottles   in   order   to   preserve  the 
strength  of  the  solution  unimpaired.     Four  qualities  are  gen- 
erally  found   in   commerce,   viz.,   ammonia    of   0.910    specific 
gravity  (containing  24.2  per  cent,  of  ammonia  gas)  ;   of  0.920 
specific   gravity   (with   21.2    per    cent,    of    ammonia   gas^  ;   of 
0.940  specific  gravity  (with  15.2   percent,   of  ammonia  gas); 
and  0.960  specific   gravity   (with   9.75   per  cent,   of  ammonia 
gas).     It  is  employed   for  neutralizing  nickel  and  cobalt  baths 
when  too  acid,  in  the  preparation  of  fulminating  gold,  and  as 
an  addition  to  some  copper  and  brass  baths. 

Recognition. —  By  the  odor. 

13.  Calcium  hydrate  (burnt  or  quick  lime). — It  forms  hard, 
white  to  gray  pieces,  which  on  moistening  with  water  crumble 
to  a  light  white  powder,  evolving  thereby  much  heat.     Vienna 
lime  is  burnt  lime  containing  magnesia.     Lime  serves  for  free- 
ing objects  from  grease,  and   for  this  purpose  is  made  into  a 
thinly-fluid   paste  with  chalk  and  water  with  which  the  objects 
to  be  freed   from   grease  are  brushed.     Vienna  lime  is  much 
used  as  a  polishing  agent. 

III.  Sulphur  Combinations. 

14.  Sulphuretted  hydrogen   (sulphydric  acid,  hydro  sulphuric 
acid). — A  very  poisonous  colorless  gas  with  a  fetid  smell  re- 
sembling that  of  rotten  eggs.     Ignited  in  the  air  it  burns  with  a 
blue  flame,  sulphurous  acid  and  water  being  formed.     At  the 
ordinary  temperature  water  absorbs  about  three  times  its  own 
volume  of  the  gas,  and  then  acquires  the  same  properties  as  the 
gas  itself.     Sulphuretted  hydrogen  serves  for  the  metallizing  of 
moulds  as  described  on  p.  393,  where  the  manner  of  evolving 
it  is  also  given.     It  is  sometimes  employed  for  the  production 
of  "oxidized"  silver.     Bringing  not  only  metallic  salts,  but  gilt 
or  silvered  articles,  or  pure  gold  and  silver,  in  contact  with  sul- 
phuretted hydrogen,  should  be  carefully  avoided,  they  being 
rapidly  sulphurized  by  it. 


430  ELECTRO-DEPOSITION    OF   METALS. 

Recognition. — By  its  penetrating  smell;  further,  by  a  strip  of 
paper  moistened  with  sugar  of  lead  solution  becoming  black 
when  brought  into  a  solution  or  an  atmosphere  containing  sul- 
phuretted hydrogen. 

15.  Potassium  sulphide  (liver  of  sulphur}. — It  forms  a  hard 
green-yellow  to  pale  brown  mass,  with  conchoidal  fracture ;    it 
readily  absorbs  moisture,  whereby  it  deliquesces  and  smells  of 
sulphuretted   hydrogen.     It  is  employed   for  coloring  copper 
and  silver  black. 

Recognition. — On  pouring  an  acid  over  liver  of  sulphur  sul- 
phuretted hydrogen  is  evolved  with  effervescence,  sulphur  be- 
ing at  the  same  time  separated. 

1 6.  Ammonium    sulphide   (sulp  hydrate  or  hydrosulphate  of 
ammonia). — When  freshly  prepared  it  forms  a  clear  and  color- 
less fluid,  with  an  odor  of  ammonia  and  sulphuretted  hydrogen  ; 
by  standing  'it  becomes  yellow,  and,  later  on,  precipitates  sul- 
phur.    It  is  used  for  the  same  purpose  as  liver  of  sulphur. 

17.  Carbon  disulphide  or  bisulphide. — Pure  carbon  disulphide 
is  a  colorless   and  transparent  liquid,  which  is  very  dense,  and 
exhibits  the  property  of  double  refraction.     Its  smell  is  charac- 
teristic  and  most  disgusting,  and  may  be  compared  to  that  of 
rotten  turnips.     It  burns  with  a  blue  flame  of  sulphurous  acid, 
carbonic  acid  being  at  the  same  time   produced.     It  is  used  as 
a  solvent  for  phosphorus  and  caoutchouc  in  metallizing  moulds 
according  to  Parkes's   method.     This  solution  should  be  very 
carefully  handled. 

1 8.  Antimony    sulphide. — a.    Black    sulphide    of    antimony 
(stibium  sulfuratum  nigrum}  is  found  in  commerce  in  heavy, 
gray,  and  lustreless  pieces  or  as  a  fine  black-gray  powder,  with 
slight  lustre.     It  serves  for  the  preparation  of  antimony  baths, 
and  for  coloring  copper  alloys  black. 

b.  Red  sulphide  of  antimony  (stibium  sulfuratum  auran- 
tiacum)  forms  a  delicate  orange-red  powder  without  taste  or 
odor;  it  is  insoluble  in  water,  but  soluble  in  ammonium  sul- 
phide, spirits  of  hartshorn,  and  alkaline  lyes.  In  connection 
with  ammonium  sulphide  or  ammonia  it  serves  for  coloring 
brass  brown. 


CHEMICAL    PRODUCTS.  431 

19.  Arsenic  trisulphide  or  arsenious  sulphide  (orpimenf). — It 
is  found  in  commerce  in  the  natural  as  well  as  artificial  state, 
the  former   occurring   mostly   in   kidney-shaped   masses   of    a 
lemon  color,  and  the  latter  in  more  orange-red  masses,  or  as  a 
dull  yellow  powder.     Specific  gravity  3.46.     It  is  soluble  in  the 
alkalies  and  spirits  of  sal  ammoniac. 

20.  Ferric  sttlphide. — Hard   black   masses   generally   in   flat 
plates,  which  are  only  used   for  the  evolution   of  sulphuretted 
hydrogen. 

IV.   Chlorine  Combinations. 

21.  Sodium  chloride  {common  salt,  rock  salt). — The  pure  salt 
should  form  white  cubical  crystals,  of  which  100  parts  of  cold 
water   dissolve   36,   hot   water   dissolving   slightly  more.     The 
specific  gravity  of   sodium   chloride   is   2.2.     In  electroplating 
sodium  chloride  is  employed  as  a  conducting  salt  for  some  gold 
baths,  as  a  constituent  of  argentiferous  pastes,  and  for  precipi- 
tating the  silver  as  chloride  from  argentiferous  solutions. 

Recognition. — An  aqueous  solution  of  sodium  chloride  on 
being  mixed  with  a  few  drops  of  lunar  caustic  solution  yields  a 
white  caseous  precipitate,  which  becomes  black  by  exposure  to 
light  and  does  not  dissapear  by  the  addition  of  nitric  acid,  but 
is  dissolved  by  ammonia  in  excess. 

22.  Ammonium  chloride  (sal ammoniac) . — A  white  substance 
found  in  commerce  in  the  shape  of  tough   fibrous  crystals.     It 
has  a  sharp  saline  taste,  and  is  soluble  in  2  ^  parts  of  cold,  and 
in  a  much  smaller  quantity  of  hot  water.     By  heat  it  is  sub- 
limed without  decomposition.     It  serves  for  soldering  and  tin- 
ning, and  as  a  conducting  salt  for  many  baths. 

Recognition. — By  the  sublimation  on  heating.  By  adding  to 
a  saturated  solution  of  the  salt  a  few  drops  of  solution  of  plati- 
num chloride,  a  yellow  precipitate  of  platoso-ammonium 
chloride  is  formed. 

23.  Antimony  trichloride  (butter  of  antimony}. — A  crystalline 
mass  which  readily  deliquesces  in  the  air.     Its  solution  in  hydro- 
chloric acid  yields  the  liquor  stibii  chlorati,  also  called  liquid 


432  ELECTRO-DEPOSITION   OF    METALS. 

butter  of  antimony;  it  has  a  yellowish  color,  and  on  mixing 
with  water  yields  an  abundant  white  precipitate,  soluble  in 
potash  lye.  The  solution  serves  for  coloring  brass  steel  gray, 
and  for  browning  gun-barrels. 

24.  Arsenious  chloride. — A  thick  oily  fluid,  which  evaporates 
in  the  air  with  the  emission  of  white  vapors. 

25.  Copper  chloride. — Blue-green  crystals  readily   soluble  in 
water.     The  concentrated  solution  is  green,  and  the  dilute  solu- 
tion blue.     On  evaporating  to  dryness,  brown-yellow  copper 
chloride  is  formed.     It  is  employed  in  copper  and  brass  baths 
as  well  as  for  patinizing. 

26.  Tin  chloride. — a.  Stannous  chloride  or  tin  salt.     A  white 
crystalline  salt  readily  soluble  in  water,  but  its  solution  on  ex- 
posure to  the  air  becomes  turbid ;   by  adding,  however,  hydro- 
chloric acid,  it  again  becomes  clear.     On  fusing  the  crystallized 
salt  it  loses  its  water  of  crystallization,  and  forms  a  solid  non- 
transparent  mass  of  a  pale-yellow   color — the  fused   tin  salt. 
The  crystallized,  as  well  as  the  fused,  salt  serves  for  the  prepa- 
ration of  brass,  bronze,  and  tin  baths. 

Recognition. — By  pouring  hydrochloric  acid  over  a  small 
quantity  of  tin  salt  and  adding  potassium  chromate  solution, 
the  solution  acquires  a  green  color.  By  mixing  dilute  tin  salt 
solution  with  some  chlorine  water  and  adding  a  few  drops  of 
gold  chloride  solution,  purple  of  Cassius  is  precipitated  ;  very 
dilute  solutions  acquire  a  purple  color. 

b.  Stannic  chloride  occurs  in  commerce  in  colorless  crystals, 
and  in  the  anhydrous  state  forms  a  yellowish,  strongly  fuming 
caustic  liquid  known  as  the  "  fuming  liquor  of  Libadius." 

27.  Zinc  chloride  (hydrochlorate  or  muriate  of  zinc;  butter  of 
zinc}. — A  white  crystalline  or  fused  mass  which  is  very  soluble 
and  deliquescent.     The  salt  prepared  by  evaporation  generally 
contains  some  zinc  oxychloride,  and  hence  does  not  yield  an 
entirely  clear  solution.     It  serves  for  preparing  brass  and  zinc 
baths,  and    its   solution    for   nickeling    by   immersion,   solder- 
ing, etc. 

Recognition. — Solution  of  caustic  potash  separates  a  volum- 


CHEMICAL   PRODUCTS.  433 

inous  precipitate  of  zinc  oxyhydrate,  which  redissolves  in  an 
excess  of  the  caustic  potash  solution.  By  conducting  sul- 
phuretted hydrogen  into  a  solution  of  a  zinc  salt  acidulated 
with  acetic  acid,  a  precipitate  of  white  zinc  sulphide  is  formed. 

28.  Zinc  chloride  and  ammonium  chloride. — This   salt  is  a 
combination  of  zinc  chloride  with  sal  ammoniac,  and  forms  a 
white  very  deliquescent  powder.     Its  solution  serves  for  solder- 
ing and  for  zincking  by  contact. 

29.  Nickel  chloride. — It  is  found   in  commerce   in  the  shape 
of  deep  green  crystals  and  of  a  pale  green  powder ;   the  latter 
contains  considerably  less  water  and   less  free   acid   than  the 
crystallized  article,  and  is  to  be  preferred  for  electro-plating 
purposes.     The  crystallized  salt  dissolves  readily  in  water,  and 
the  powder  somewhat  more  slowly;   should  the  solution  of  the 
latter  deposit  a  yellow  precipitate,  consisting   of   basic   nickel 
chloride,  it  has  to   be  brought  into  solution  by  the  addition  of 
a  small  quantity  of  hydrochloric  acid.     Nickel  chloride  is  em- 
ployed for  nickel  baths. 

Recognition. — By  mixing  the  green  solution  of  the  salt  with 
some  spirits  of  sal  ammoniac,  a  precipitate  is  formed  which 
dissolves  in  an  excess  of  spirits  of  sal  ammoniac,  the  solution 
showing  a  deep  blue  color. 

30.  Cobalt  chloride. — It   forms   small    rose-colored   crystals, 
which,  on  heating,  yield  their  water  of  crystallization  and  are 
converted  into  a  blue  mass.     The  crystals  are  readily  soluble 
in  water,  while   the   anhydrous   blue  powder  dissolves  slowly. 
Cobalt   chloride   is   employed   for    the    preparation    of    cobalt 
baths. 

Recognition. — Caustic  potash  precipitates  from  a  solution  of 
cobalt  chloride  a  blue  basic  salt  which  is  gradually  converted 
into  a  rose-colored  hydrate,  and,  with  the  access  of  air,  into 
green-brown  cobaltous  hydrate ;  the  aqueous  solution  yields 
with  solution  of  yellow  prussiate  of  potash  a  pale  gray-green 
precipitate. 

31.  Silver  chloride  (horn  silver). — A  heavy   white    powder 
gradually    passing,    by    exposure    to    white    light,    through    a 

28 


434  ELECTRO-DEPOSITION    OF   METALS. 

gradation  of  shades  from  violet  to  black.  By  precipitation 
from  silver  solutions  it  separates  as  a  caseous  precipitate  (p. 
285).  At  500°  F.  it  melts,  without  decomposing,  to  a  yellow- 
ish fluid,  which,  on  cooling,  congeals  to  a  transparent,  tena- 
cious, horn-like  mass.  Chloride  of  silver  is  practically  insoluble 
in  water,  but  dissolves  readily  in  spirits  of  sal  ammoniac  and 
in  potassium  cyanide  solution.  It  is  employed  in  the  prepara- 
tion of  baths  for  electro-silvering,  for  the  whitening  baths,  and 
for  the  pastes  for  silvering  by  friction. 

Recognition. — By  its  solubility  in  ammonia,  pulverulent  me- 
tallic silver  being  separated  from  the  solution  by  dipping  in  it 
bright  ribands  of  copper. 

32.  Gold  chloride  (terchloride  of  gold,  muriate  of  gold,  auric 
chloride). — This  salt  occurs  in  commerce  as  crystallized   gold 
chloride  of  an  orange-yellow  color,  and  as  a  brown  crystalline 
mass,  which  is  designated  as  neutral  gold  chloride,  or  as  gold 
chloride  free  from  acid,  while  the  crystallized  article  always  con- 
tains acid,  and,  hence,  should  not  be  used  for  gold  baths.     Gold 
chloride  absorbs  atmospheric  moisture  and  becomes  resolved 
into  a  liquid  of  a  fine  gold  color.     On  being  moderately  heated 
yellowish-white  aurous  chloride  is  formed,  and  on  being  sub- 
jected to  stronger  heat  it  is  decomposed  to  metallic  gold  and 
chlorine  gas.     By  mixing  its  aqueous  solution  with  ammonia,  a 
yellow-brown  powder  consisting  of  fulminating  gold is  formed. 
In  a  dry  state  this  powder  is  highly  explosive,  and,  hence,  when 
precipitating  it  from  gold  chloride  solution  for  the  preparation 
of  gold  baths,  it  must  be  used  while  still  moist. 

Recognition. — By  the  formation  of  the  precipitate  of  fulmi- 
nating gold  on  mixing  the  gold  chloride  solution  with  ammonia. 
Further  by  the  precipitation  of  brown  metallic  gold  powder  on 
mixing  the  gold  chloride  solution  with  green  vitriol  solution. 

33.  Platinic  chloride. — The  substance  usually  known  by  this 
name  is  hydroplatinic  chloride.     It  forms  red-brown  very  sol- 
uble— and    in    fact    deliquescent — crystals.     With    ammonium 
chloride   it    forms   platoso-ammonium  chloride   (see   p.   319). 
Both   combinations  are  used   in   the   preparation   of  platinum 


CHEMICAL   PRODUCTS.  435 

baths.     The  solution  of  platinic  chloride  also  serves  for  color- 
ing silver,  tin,  brass,  and  other  metals. 

Recognition. — By  the  formation  of  a  precipitate  of  yellow 
platoso-ammonium  chloride  by  mixing  concentrated  platinic 
chloride  solution  with  a  few  drops  of  saturated  sal  ammoniac 
solution. 

V.   Cyanides. 

34.  Potassium  cyanide  {white  prussiate  of  potash). — For 
electro-plating  purposes  pure  potassium  cyanide  with  98  to  99 
per  cent.,  as  well  as  that  containing  80,  70,  and  60  per  cent.,  is 
used,  whilst  for  pickling  the  preparation  with  45  per  cent,  is 
employed.  For  the  preparation  of  alkaline  copper  and  brass 
baths,  as  well  as  silver  baths,  the  pure  98  to  99  per  cent,  pro- 
duct is  generally  employed.  However,  for  preparing  gold 
baths  the  60  per  cent,  article  is  mostly  preferred,  because  the 
potash  present  in  all  potassium  cyanide  varieties  with  a  lower 
content  renders  fresh  baths  more  conductive.  However,  gold 
baths  may  also  be  prepared  with  98  per  cent,  potassium  cyanide 
without  fear  of  injury  to  the  efficiency  of  the  baths,  while,  under 
ordinary  circumstances,  a  preparation  with  less  than  98  per 
cent  may  safely  be  used  for  the  rest  of  the  baths.  However, 
when  potassium  cyanide  has  to  be  added  to  the  baths,  as  is 
from  time  to  time  necessary,  only  the  pure  preparation  free 
from  potash  should  be  used,  because  the  potash  contained  in 
the  inferior  qualities  gradually  thickens  the  bath  too  much. 

No  product  is  more  important  to  the  electro-plater  than 
potassium  cyanide.  The  pure  98  to  99  per  cent,  product  is  a 
white  transparent  crystalline  mass,  the  crystalline  structure  be- 
ing plainly  perceptible  upon  the  fracture.  In  a  dry  state  it  is 
odorless,  but  when  it  has  absorbed  some  moisture  it  has  a 
strong  smell  of  prussic  acid.  It  is  readily  soluble  in  water,  and 
should  be  dissolved  in  cold  water  only,  since  when  poured  into 
hot  water  it  is  partially  decomposed,  which  is  recognized  by 
the  appearance  of  an  odor  of  ammonia.  Potassium  cyanide 
solution  in  cold  water  may,  however,  be  boiled  for  a  short  tfme 


436  ELECTRO-DEPOSITION    OF   METALS. 

without  suffering  essential  decomposition.  Potassium  cyanide 
must  be  kept  in  well-closed  vessels,  being  when  exposed  to  the 
air  deliquescent,  and  it  is  decomposed  by  the  carbonic  acid  of 
the  air,  whereby  potassium  carbonate  is  formed  while  prussic 
acid  escapes.  It  is  a  deadly  poison  and  must  be  used  with  the 
utmost  caution.  Potassium  cyanide  with  80,  70,  60,  or  45  per 
cent,  forms  a  gray-white  to '  white  mass  with  a  porcelain-like 
fracture.  A  pale  gray  coloration  is  not  a  proof  of  impurities, 
it  being  due  to  somewhat  too  high  a  temperature  in  fusing. 
These  varieties  are  found  in  commerce  in  irregular  lumps  or  in 
sticks,  the  use  of  the  latter  offering  no  advantage.  Their  be- 
havior towards  the  air  and '  in  dissolving  is  the  same  as  that  of 
the  pure  product. 

Recognition. — By  the  bitter  almond  smell  of  the  solution.  By 
mixing  potassium  cyanide  solution  with  ferric  chloride  and  then 
with  hydrochloric  acid  until  the  latter  strongly  predominates,  a 
precipitate  of  Berlin  blue  is  formed. 

The  pure  salt  free  from  potash  does  not  effervesce  on  adding 
dilute  acid,  which  is,  however,  the  case  with  the  inferior 
qualities. 

To  facilitate  the  use  of  potassium  cyanide  with  a  different 
content  than  that  given  in  a  formula  for  preparing  a  bath,  the 
following  table  is  here  given : — 

Potassium  cyanide  with 


98  per  cent. 

80  per  cent. 

70  per  cent. 

60  per  cent. 

45  per  cent. 

By  weight. 
i          part   = 
0.820     "      = 
0.714     «      = 
0.615     "      = 
0.460    "      = 

By  weight. 
=    1.230  paits    = 
=    i             " 

=  0-875    Part    = 
=  0.750     •« 
=  0.562      " 

By  weight. 
=    1.400   parts    = 

=    I-I43      " 
=    I.          part     = 
=   0.857      " 
=   0.643      " 

By  weight. 
=    i.  660  parts   = 

=    1-333      "       = 
=    1.170      "       = 
=    I.           part    = 
=   0.750       "      = 

By  weight. 
=    2.180  parts. 
=    1.780     " 
=    i-S^o      " 

=    i-45°     " 
=    i          part. 

35.  Copper  cyanides. — There  is  a  cuprous  and  a  cupric  cya- 
nide ;  that  used  for  electro-plating  purposes  being  a  mixture  of 
both.  It  is  a  green-brown  powder,  which  should  not  be  dried, 


CHEMICAL   PRODUCTS.  •       437 

since  in  the  moist  state  it  dissolves  more  readily  in  potassium 
cyanide.  It  is  only  used  as  a  double  salt,  i.  e.y  in  combination 
with  potassium  cyanide  in  the  preparation  of  copper,  brass, 
tombac,  and  red  gold  baths. 

Recognition. — By  evaporating  a  piece  of  copper  cyanide  the 
size  of  a  pea,  or  its  solution  in  hydrochloric  acid  to  dryness  in 
a  water  bath,  wherein  care  must  be  taken  not  to  inhale  the 
vapors,  and  dissolving  the  residue  in  water,  a  green-blue  solu- 
tion is  obtained  which  acquires  a  deep  blue  color  by  the  addi- 
tion of  ammonia  in  excess. 

36.  Zinc  cyanide  (hydrocyanate  of  zinc,  prussiate  of  zinc). — 
A  white  powder  insoluble  in  water,  but  soluble  in  potassium 
cyanide,  ammonia  and  the  alkaline  sulphites ;   the  fresher  it  is, 
the  more  readily  it  dissolves,  the  dried  product  dissolving  with 
difficulty.      Its  solution  in  potassium  cyanide  is  used  for  brass 
baths. 

Recognition. — By  evaporating  zinc  cyanide  or  its  solution  in 
an  excess  of  hydrochloric  acid,  zinc  chloride  remains  behind, 
which  is  recognized  by  the  reaction  given  under  zinc  chloride. 

37.  Silver  cyanide  {prussiate,  or  hydrocyanate  of  silver}. — A 
white  powder  which  slowly  becomes  black  when  exposed  to 
light.     It  is  insoluble  in  water  and  cold  acids,  which,  however, 
will  dissolve  it  with  the  aid  of  heat.     At  750°  F.  it  melts  to  a 
dark  red  fluid,  which,  on  cooling,  forms  a  yellow  mass  with  a 
granular    structure.       It    is     readily    dissolved     by    potassium 
cyanide,  but  is  only  slightly  soluble   in   ammonia,  differing  in 
this  respect  from  silver  chloride.     It  forms  a  double  salt  with 
potassium  cyanide,  and  as  such  is  employed  in  the  preparation 
of  silver  baths. 

38.  Potassium  ferro-cyanide  (yellow  prussiate  of  potash}. — It 
occurs  in  the  shape  of  yellow  semi-translucent  crystals  with 
mother-of-pearl    lustre,    which    break    gradually    and    without 
noise.     For  the  solution  of  I  part  of  it,  4  of  water  are  required, 
the   solution   exhibiting  a  pale  yellow  color.     It  precipitates 
nearly  all  the  metallic  salts  from  their  solutions,  some  of  the 
precipitates   being  soluble   in   an   excess  of  the  precipitating 


43 8  ELECTRO-DEPOSITION    OF   METALS. 

agent.  This  salt  is  not  poisonous.  It  serves  for  the  prepara- 
tion of  silver  and  gold  baths  ;  its  employment,  however,  offering 
no  advantages  over  potassium  cyanide  except  its  non-poisonous 
properties  be  considered  as  such. 

Recognition. — When  the  yellow  solution  is  mixed  with  ferric 
chloride  a  precipitate  of  Berlin  blue  is  formed. 

VI.   Carbonates. 

39.  Potassium  carbonate  (potash). — It  is  found  in  commerce 
in   gray-white,  bluish,  yellowish  pieces,  the   colorations  being 
due  to  admixtures  of  small  quantities  of  various  metallic  oxides, 
and  pure  in  the  form  of  a  white  powder  or  in  pieces  the  size  of 
a  pea.     The  salt,  being  very  deliquescent,  has  to  be  kept  in 
well-closed  receptacles.     It  is  readily  soluble,  and,  if  pure,  the 
solution   in  distilled  water  must  be  clear.     It  serves  as  an  ad- 
dition to  some  baths,  and  in  an  impure  state  for  freeing  objects 
from  grease. 

Recognition. — The  solution  effervesces  on  the  addition  of 
hydrochloric  acid.  The  solution  neutralized  with  hydrochloric 
acid  gives  with  platinum  chloride  a  heavy  yellow  precipitate, 
provided  the  solution  be  not  too  dilute. 

40.  Acid  potassium  carbonate  or  monopotassic  carbonate,  com- 
monly called  bicarbonate  of  potash. — Coloiless  transparent  crys- 
tals, which  at  a  medium  temperature  dissolve  to  a  clear  solution 
in  4  parts  of  water.     It  is  not  deliquescent ;   however,  on  boil- 
ing its  solution  it  loses  carbonic  acid,  and  contains   then  only 
potassium  carbonate.     It  is  employed  for  the  preparation  of 
certain  baths  for  gilding  by  simple  immersion. 

41.  Sodium  carbonate  (washing  soda). — It  occurs  in  com- 
merce as  crystallized  or  calcined  soda  of  various  degrees  of 
purity.     The  crystallized   product  forms  colorless   crystals  or 
masses  of  crystals,  which,  on  exposure  to  air,  rapidly  effloresce 
and  crumble  to  a  white  powder.     By  heating,  the  crystals  also 
lose  their  water,  a  white  powder,  the  so-called  calcined  soda, 
remaining  behind.     Soda  dissolves  readily  in  water,  and  serves 
as  an  addition  to  copper  and  brass  baths,  for  the  preparation 


CHEMICAL    PRODUCTS.  439 

of  metallic  carbonates,  and  for  freeing  objects  from  grease,  the 
ordinary  impure  soda  being  used  for  the  latter  purpose. 

The  directions  for  additions  of  sodium  carbonate  to  baths 
generally  refer  to  the  crystallized  salt.  If  calcined  soda  is  to 
be  used  instead,  0.4  part  of  it  will  have  to  be  taken  for  I  part 
of  the  crystallized  product. 

42.  Sodium    bicarbonate    (baking   powder). — A    dull    white 
powder  soluble  in  10  parts  of  water  of  68°  F.     On  boiling,  the 
solution  loses  one-half  of  its  carbonic  acid,  and  then  contains 
sodium  carbonate  only. 

43.  Calcium  carbonate  (marble,  chalk}. — When  pure  it  forms 
a  snow-white  crystalline  powder,  a  yellowish  color  indicating  a 
content  of  iron.     It  is  insoluble  in  water,  but  soluble,  with  effer- 
vescence, in  hydrochloric,  nitric,  and  acetic  acids.     In  nature, 
calcium  carbonate  occurs  as  marble,  limestone,  chalk. 

In  the  form  of  whiting  (ground  chalk  carefully  freed  from  all 
stony  matter)  it  is  used  for  the  removal  of  an  excess  of  acid  in 
acid  copper  baths,  and  mixed  with  burnt  lime  as  an  agent  for 
freeing  objects  from  grease. 

44.  Copper  carbonate. — Occurs   in   nature  as  malachite  and 
allied  minerals.     The  artificial  carbonate  is  an  azure-blue  sub- 
stance, insoluble  in  water,  but  soluble,  with  effervescence,  in 
acids.     Copper   carbonate   precipitated   from   copper   solution 
by  alkaline  carbonates  has  a  greenish  color.     Copper  carbon- 
ate  is  employed  for  copper  and  brass  baths,  and  for  the  re- 
moval of  an  excess  of  acid  in  acid  copper  baths. 

Recognition. — Dissolves  in  acids  with  effervescence;  on  dip- 
ping a  riband  of  bright  sheet-iron  in  the  solution,  copper 
separates  upon  the  iron.  On  compounding  the  solution  with 
ammonia  in  excess,  a  deep  blue  coloration  is  obtained. 

45.  Zinc  carbonate. — A  white   powder,   insoluble   in  water. 
The  product  obtained  by  precipitating  a  zinc  salt  with  alkaline 
carbonates  is  a  combination  of  zinc  carbonate  with  zinc  oxy- 
hydrate.     It  serves  for  brass  baths  in  connection  with  potassium 
cyanide. 

Recognition. — In   a  solution   in  hydrochloric   acid,   which  is 


44°  ELECTRO-DEPOSITION    OF   METALS. 

formed   with  effervescence,   according  to   the   reactions  given 
under  zinc  chloride  (27). 

46.  Nickel  carbonate. — A  pale  apple-green  powder,  insoluble 
in  water,  but  soluble,  with  effervescence,  in  acids.     It   is   em- 
ployed for  neutralizing  nickel  baths  which  have  become  acid. 

Recognition. — In  hydrochloric  acid,  it  dissolves,  with  effer- 
vescence, to  a  green  fluid ;  by  the  addition  of  a  small  quantity 
of  ammonia,  nickel  oxyhydrate  is  precipitated,  which,  by  add- 
ing ammonia  in  excess,  is  redissolved,  the  solution  showing  a 
blue  color. 

47.  Cobalt  carbonate. — A  reddish  powder,  insoluble  in  water, 
but  soluble  in  acids,  the  solution  forming  a  red  fluid. 

VII.  Sulphates  and  Sulphites. 

48.  Sodium  sulphate  (Glaubers  salt). — Clear  crystals  of  a 
slightly  bitter  taste,  which   effloresce  by  exposure  to  the  air. 
They  are  readily  soluble  in  water.     On   heating,  the  crystals 
melt  in  their  water  of  crystallization,  and  on  glowing,  calcined 
Glauber's  salt  remains  behind.     It  is   used  as  an  addition  to 
some  baths. 

49.  Ammonium  sulphate. — It  forms  a  neutral  colorless  salt, 
which   is  constant  in  the  air,  readily  dissolves   in  water,  and 
evaporates   on    heating.     It    serves   as   a   conducting    salt    for 
nickel,  cobalt,  and  zinc  baths. 

Recognition. — By  its  evaporating  on  heating;  a  concentrated 
solution  compounded  with  platinic  chloride  gives  a  yellow  pre- 
cipitate of  platoso-ammonium  chloride,  while  a  solution  mixed 
with  a  few  drops  of  hydrochloric  acid  gives  with  barium  chlo- 
ride a  precipitate  of  barium  sulphate. 

50.  Aluminium-potassium    sulphate    (potash-alum). — Color- 
less crystals  or  pieces  of  crystals  with  an  astringent  taste.     It  is 
soluble  in  water,  12  parts  of  it  dissolving  in  100  parts  of  water 
at  the  ordinary  temperature.     On  heating,  the  crystals  melt, 
and  are  converted   into   a   white   spongy  mass,   the   so-called 
burnt  alum.     Potash-alum  serves  for  the  preparation  of  zinc 
baths  and  for  brightening  the  color  of  gold. 


CHEMICAL    PRODUCTS.  441 

Recognition. — On  adding  sodium  phosphate  to  the  solution  a 
jelly-like  precipitate  of  aluminium  phosphate  is  formed,  which 
is  soluble  in  caustic  potash,  but  insoluble  in  acetic  acid. 

51.  Ammonium- alum  is  exactly  analogous  to  the  above,  the 
potassium  sulphate  being  simply  replaced   by  ammonium  sul- 
phate.    It  is  for  most  purposes  interchangeable  with  potash- 
alum.     On  glowing  ammonium-alum  the  ammonium  sulphate 
is  lost,  pure  alumina  remaining  behind.     Ammonium-alum  is 
used  for  preparing  a  bath  for  zincking  iron  and  steel  by  im- 
mersion. 

Recognition. — The  same  as  potash-alum.  On  heating  the 
comminuted  ammonium-alum  with  potash  lye  an  odor  of  am- 
monia becomes  perceptible. 

52.  Iron  sulphate  (iron  protosulphate,  ferrous  sulphate  or  green 
vitriol). — Pure    green    vitriol    forms    bluish- green    transparent 
crystals  of  a  sweetish  astringent  taste,  which  readily  dissolve  in 
water.     Crude  green  vitriol   is  a  green   crystalline   substance, 
often  yellowish  on  the  exterior  owing  to  the  formation  of  ferric 
compounds  with  the  aid  of  atmospheric  oxygen.     It  generally 
contains,  besides  ferrous  sulphate,  the  sulphates  of  copper  and 
zinc  as  well  as  ferric  sulphate.     On  account  of  the  tendency  to 
peroxidation,  green  vitriol  and  other  ferrous  compounds  should 
not  be  exposed  to  the  air  any  more  than  is  necessary.     Green 
vitriol  is  employed  for  the  preparation  of  iron  baths,  and  for 
the  reduction  of  gold  from  its  solutions. 

Recognition, — By  compounding  the  green  solution  with  a  few 
drops  of  concentrated  nitric  acid,  a  black-blue  ring  is  formed  on 
the  point  of  contact.  On  mixing  the  lukewarm  solution  with 
gold  chloride,  gold  is  separated  as  a  brown  powder,  which  by 
rubbing  acquires  the  lustre  of  gold. 

53.  Iron- ammonium  sulphate. — Green  crystals  which  are  con- 
stant in  the  air  and  do  not  oxidize  as  readily  as  green  vitriol. 
100  parts  of  water  dissolve  16  parts  of  this  salt.     It  is  used  for 
the  same  purposes  as  green  vitriol. 

54.  Copper   sulphate    (cupric    sulphate   or   blue    vitriol}. — It 
forms  blue  crystals,  of  which  100  parts  of  cold  water  dissolve 


442  ELECTRO- DEPOSITION    OF    METALS. 

about  40,  and  the  same  volume  of  hot  water  about  200  parts. 
Blue  vitriol  which  does  not  possess  a  pure  blue  color,  but 
shows  a  greenish  lustre,  is  contaminated  with  green  vitriol,  and 
should  not  be  used  for  electro-plating  purposes.  Blue  vitriol 
serves  for  the  preparation  of  alkaline  copper  and  brass  baths, 
acid  copper  baths,  etc. 

Recognition. — By  its  appearance,  as  it  can  scarcely  be  mis- 
taken for  anything  else.  A  content  of  iron  is  recognized  by 
boiling  blue  vitriol  solution  with  a  small  quantity  of  nitric  acid, 
and  adding  spirits  of  sal  ammoniac  in  excess ;  brown  flakes  in- 
dicate iron. 

55.  Cuprous  sulphite. — A  brownish   red   crystalline   powder 
formed  by  treating  cuprous  hydrate  with  sulphurous  acid  solu- 
tion.    It  is  insoluble  in  water,  but  readily  soluble  in  potassium 
cyanide,  with  only  slight  evolution  of  cyanogen.     It  serves  for 
the    preparation   of   alkaline    copper    baths   in   place   of   basic 
acetate  of  copper  (verdigris),  copper  vitriol,  or  cuprous  oxide. 

56.  Zinc  sulphate  (white  vitriol}. — It  forms  small  colorless 
prisms  of  a  harsh  metallic  taste,  which  readily  oxidize  on  ex- 
posure to  the  air.     By  heating  the  crystals  melt,  and  by  glow- 
ing are  decomposed   into  sulphurous  acid  and   oxygen,  which 
escape,  while  zinc  oxide  remains  behind  as  residue.      100  parts 
of  water  dissolve  about  50  parts  of  zinc  sulphate  in  the  cold, 
and  nearly  100  at  the  boiling-point.     Zinc  sulphate  is  employed 
for  the  preparation  of  brass  and  zinc  baths. 

Recognition. — By  mixing  zinc  sulphate  solution  with  acetic 
acid  and  conducting  sulphuretted  hydrogen  into  the  mixture,  a 
white  precipitate  of  zinc  sulphide  is  formed.  A  slight  content 
of  iron  is  recognized  by  the  zinc  sulphate  solution,  made  alka- 
line by  ammonia,  giving  with  ammonium  sulphide  a  somewhat 
colored  precipitate  instead  of  a  pure  white  one.  However,  a 
slight  content  of  iron  does  no  harm. 

57.  Nickel  sulphate. — Beautiful  dark  green  crystals,  readily 
soluble  in  water,  the  solution   exhibiting  a  green   color.     On 
heating  the  crystals  to  above  536°  F.,  yellow  anhydrous  nickel 
sulphate  remains  behind.     Like  the  double  salt  described  be- 


CHEMICAL    PRODUCTS.  443 

low,  it  serves  for  the  preparation  of  nickel  baths  and  for  color- 
ing zinc. 

Recognition. — By  compounding  the  solution  with  ammonia 
the  green  color  passes  into  blue.  Potassium  carbonate  pre- 
cipitates pale  green  basic  nickel  carbonate,  which  dissolves  on 
adding  ammonia  in  excess,  the  solution  showing  a  blue  color. 
A  content  of  copper  is  recognized  by  the  separation  of  black- 
brown  copper  sulphide  on  introducing  sulphuretted  hydrogen 
into  the  heated  solution  previously  strongly  acidulated  with 
hydrochloric  acid. 

58.  Nickel- ammonium  sulphate. — It  forms  green  crystals  of  a 
somewhat  paler  color  than  nickel  sulphate.     This  salt  dissolves 
with  more  difficulty  than  the  preceding,  100  parts  of  water  dis- 
solving only  5.5  parts  of  it.     It  is  used  for  the  same  purposes 
as  the   nickel   sulphate,   and    is   also   recognized   in   the   same 
manner. 

59.  Cobalt  sulphate. — Crimson   crystals  of  a  sharp  metallic 
taste,  which  are  constant  in  the  air  and  readily  dissolve  in  water, 
the  solution  showing  a  red  color.     By  heating,  the  crystals  lose 
their  water  of  crystallization  without,  however,  melting,  and  be- 
come thereby  transparent  and  rose-colored.     The  salt  is  used 
for  cobalt  baths  for  electro-cobalting  and  cobalting  by  contact. 

Recognition. — In  the  presence  of  ammoniacal  salts,  caustic 
potash  precipitates  a  blue  basic  salt,  which,  on  heating,  changes 
to  a  rose-colored  hydrate,  and  by  standing  for  some  time  in  the 
air  to  a  green-brown  hydrate.  By  mixing  a  concentrated  solu- 
tion of  the  salt  strongly  acidulated  with  hydrochloric  acid  with 
solution  of  potassium  nitrate,  a  reddish-yellow  precipitate  is 
formed. 

60.  Cob  alt- ammonium  sulphate. — This  salt  forms  crystals  of 
the  same  color   as   cobalt   sulphate,  which,  however,  dissolve 
more  readily  in  water. 

61.  Sodium    sulphite    and    bisulphite. — a.    Sodium   sulphite. 
Clear,  colorless,  and  odorless  crystals,  which  are  rapidly  trans- 
formed into  an  amorphous  powder  by  efflorescence.     The  salt 
readily  dissolves  in  water,  the  solution  showing  a  slight  alkaline 


444  ELECTRO-DEPOSITION    OF   METALS. 

reaction  due  to  a  small  content  of  sodium  carbonate.  It  is  em- 
ployed in  the  preparation  of  gold,  brass,  and  copper  baths,  for 
silvering  by  immersion,  etc. 

Recognition. — The  solution  when  mixed  with  dilute  sulphuric 
acid  has  an  odor  of  burning  sulphur. 

b.  Sodium  bisulphite.  Small  crystals,  or  more  frequently  in 
the  shape  of  a  pale  yellow  powder  with  a  strong  odor  of  sul- 
phurous acid  and  readily  soluble  in  water.  The  solution 
shows  a  strong  acid  reaction  and  loses  sulphurous  acid  in  the 
air.  It  is  employed  in  the  preparation  of  alkaline  copper  and 
brass  baths. 

Both  the  sulphite  and  bisulphite  must  be  kept  in  well-closed 
receptacles,  as  by  the  absorption  of  atmospheric  oxygen  they 
are  converted  to  sulphate. 

VIII.  Nitrates. 

62.  Potassium  nitrate  (saltpetre,  nitre}. — It  forms  large,  pris- 
matic crystals,  generally  hollow,  but  also  occurs  in  commerce 
in  the  form  of  a  coarse  powder,  soluble  in  4  parts  of  water  at  a 
medium  temperature.     The  solution  has  a  bitter,  saline  taste 
and  shows  a  neutral   reaction.     Potassium  nitrate   melts  at  a 
glowing  heat,  and  on  cooling  congeals  to  an  opaque,  crystalline 
mass.     It  is  employed  in  the  preparation  of  desilvering  baths 
and  for  producing  a  dead  lustre  upon  gold  and  gilding.     For 
these  purposes  it  may,  however,  be  replaced  by  the  cheaper 
sodium  nitrate,  sometimes  called  cubic  nitre  or  Chile  saltpetre. 

Recognition. — A  small  piece  of  coal  when  thrown  upon  melt- 
ing saltpetre  burns  fiercely.  When  a  not  too  dilute  solution  of 
saltpetre  is  compounded  with  solution  of  potassium  bitartrate 
saturated  at  the  ordinary  temperature,  a  crystalline  precipitate 
of  tartar  is  formed. 

63.  Sodium  nitrate  (cubic  nitre  or  Chile  saltpetre). — Color- 
less crystals,  deliquescent  and  very  soluble  in  water ;   the  solu- 
tion shows  a  neutral  reaction.     It  is  used  for  the  same  purposes 
as  potassium  nitrate. 

64.  Mercurous  nitrate. — It  forms    small,   colorless    crystals, 


CHEMICAL   PRODUCTS.  445 

which  are  quite  transparent  and  slightly  effloresce  in  the  air. 
On  heating  they  melt  and  are  transformed,  with  the  evolution 
of  yellow-red  vapors,  into  yellow-red  mercuric  oxide,  which,  on 
further  heating,  entirely  evaporates.  With  a  small  quantity  of 
water,  mercurous  nitrate  yields  a  clear  solution ;  by  the  further 
addition  of  water  it  shows  a  milky  turbidity,  which,  however, 
disappears  on  adding  nitric  acid.  It -is  employed  for  quicking 
the  zincs  of  the  elements  and  the  objects  previous  to  silvering, 
and  for  brightening  gilding.  For  the  same  purpose  is  also 
used :  — 

65.  Mercuric  nitrate. — It  is  difficult  to  obtain  this  salt  in  a 
crystallized  form.     It  is  generally  sold  in  the  form  of  an  oily, 
colorless  liquid,  which,  in  contact  with  water,  separates  a  basic 
salt.     This  precipitate  disappears  upon  the  addition  of  a  few 
drops  of  nitric  acid,  and  the  liquid  becomes  clear. 

Recognition. — A  bright  riband  of  copper  dipped  in  solution 
of  mercurous  or  mercuric  nitrate  becomes  coated  with  a  white 
amalgam,  which  dissapears  upon  heating. 

66.  Silver   nitrate    (lunar   catistic}. — This    salt   is   found   in 
commerce  in  three  forms  :   either  as  crystallized  nitrate  of  silver 
in  thin,  rhombic,   and   transparent   plates;    or   in   amorphous, 
opaque,  and  white  plates  of  fused  nitrate ;   or  in  small  cylinders 
of  white,  or  gray,  or  black  color,  according  to  the  nature  of  the 
mould  employed,  in  which  form  it  constitutes  the  lunar  caustic 
for  surgical  uses.     For  our  purposes  only  the  pure,  crystallized 
product,  free  from   acid,  should   be   employed.     The  crystals 
dissolve   readily   in   water.     In   making   solutions   of  this  and 
other  silver  salts,  only  distilled  water  should  be  used ;  all  other 
waters,  owing  to  the  presence  of  chlorine,  produce  a  cloudiness 
or  even  a  distinct  precipitate  of  silver  chloride.     In  the  heat  the 
crystals  melt  to  a  colorless,  oily  fluid,  which,  on  cooling,  con- 
geals to  a  crystalline  mass.     Silver  nitrate  is  employed   in  the 
preparation  of  chloride  and  cyanide  of  silver  for  silver  baths ; 
the  solution  in  potassium  cyanide  may  also  be  used  for  silver 
baths.     The    alcoholic    solution    is    employed    for    metallizing 
moulds. 


ELECTRO-DEPOSITION    OF    METALS. 

Recognition. — Hydrochloric  acid  and  common  salt  solution 
precipitate  from  silver  nitrate  solution  silver  chloride,  which 
becomes  black  on  exposure  to  the  light,  and  is  soluble  in 
ammonia. 

IX.  Phosphates  and  Pyrophosphates. 

67.  Sodium  phosphate.— Large,  clear  crystals,  which  readily 
effloresce,  and  whose  solution  in  water  shows  an  alkaline  reac- 
tion.    It  is  employed  in  the  preparation  of  gold  baths  and  for 
the  production  of  metallic  phosphates  for  soldering. 

Recognition. — The  dilute  solution  compounded  with  silver 
nitrate  yields  a  yellow  precipitate  of  silver  phosphate. 

68.  Sodium  pyrophosphate. — It  forms  white  crystals,  which 
are  not  subject  to  efflorescence,  and  are  soluble  in  6  parts  of 
water  at  a  medium  temperature ;   the  solution  shows  an  alka- 
line reaction.     Sodium  pyrophosphate  also  occurs  in  commerce 
in  the  form  of  an  anhydrous  white  powder,  though  it  may  here 
be  said  that   the   directions   for  preparing  baths  refer   to  the 
crystallized  salt.     It  is  employed  in   the   preparation   of  gold, 
nickel-bronze,  and  tin  baths. 

Recognition. — The  dilute  solution  compounded  with  silver 
nitrate  yields  a  white  instead  of  a  yellow  precipitate. 

69.  Ammonium  phosphate. — A  colorless  crystalline  powder 
quite  readily  soluble  in  water;  the  solution  should  be  as  neutral 
as  possible.     A  salt  smelling  of  ammonia,  as  well  as  one  show- 
ing an  acid  reaction,  should  be  rejected.     It  is  employed  in  the 
preparation  of  platinum  baths. 

X.  Salts  of  the  Organic  Acids. 

70.  Potassium  bitartrate  {cream  of  tartar}. — The  pure  salt 
forms  small  transparent  crystals  of  an  acid  taste,  and  slightly 
soluble  in  water.     The  commercial  crude  tartar  or  argol,  which 
is  a  by-product  in  the  wine  industry,  forms  gray  or  dirty  red 
crystalline  crusts.     In  finely  powdered  state,  purified  tartar  is 
called  cream  of  tartar.     It  is  employed  for  the  preparation  of 
the  whitening  silver  baths,  for  those  of  tin,  and  for  the  silvering 
paste  by  friction. 


CHEMICAL    PRODUCTS.  447 

71.  Potassium  sodium  tartrate  (Rochelle  or  Seignette  salt). — 
Clear  colorless  crystals,  constant  in  the  air,  of  a  cooling  bitter 
saline  taste,  and  soluble  in  2.5  parts  of  water  of  a  medium  tem- 
perature.    The  solution  shows  a  neutral  reaction.     This  salt  is 
employed  in  the  preparation  of  copper  baths  free  from  cyanide, 
as  well  as  of  nickel  and  cobalt  baths,  which  are  to  be  decom- 
posed in  the  single  cell  apparatus. 

Recognition. — By  the  addition  of  acetic  acid  the  solution 
yields  an  abundant  precipitate  of  tartar. 

72.  Antimony -potassium    tartrate  (tartar   emetic). — A  white 
crystalline  substance,  of  which  TOO  parts  of  cold  water  dissolve 
5   parts,  while  a  like  volume  of  hot  water  dissolves   50  parts. 
The   solution  shows  a  slightly  acid  reaction.     The  only  use  of 
this  salt  is  for  the  preparation  of  antimony  baths. 

Recognition. — The  solution  compounded  with  sulphuric, 
nitric,  or  oxalic  acid  yields  a  white  precipitate,  insoluble  in  an 
excess  of  the  cold  acid.  Sulphuretted  hydrogen  imparts  to  the 
dilute  solution  a  red  color.  Hydrochloric  acid  effects  a  pre- 
cipitate, which  is  redissolved  by  the  acid  in  excess. 

73.  Copper  acetate  (verdigris). — It  is  found  in  the  market  in 
the  form  of  dark  green  crystals  showing  an  acid  reaction,  or  of 
a  neutral  bright  green  powder. 

The  crystallized  copper  acetate  forms  opaque  dark  green 
prisms,  which  readily  effloresce,  becoming  thereby  coated  with 
a  pale  green  powder ;  they  dissolve  with  difficulty  in  water,  but 
readily  in  ammonia,  forming  a  solution  of  a  blue  color,  as  well 
as  in  potassium  cyanide  and  alkaline  sulphites 

The  neutral  copper  acetate  forms  a  blue-green  crystalline 
powder,  imperfectly  soluble  in  water,  but  readily  soluble  in 
ammonia,  forming  a  solution  of  a  blue  color. 

Copper  acetate  is  used  for  preparing  copper  and  brass  baths, 
for  the  production  of  artificial  patinas,  for  coloring,  gilding,  etc. 

74.  Lead  acetate  (sugar  of  lead). — Colorless  lustrous  prisms 
or   needles   of   a   nauseous   sweet  taste   and    poisonous.     The 
crystals  effloresce  in  the  air,  melt  at  104°  F.,  and  are  readily 
soluble    in   water,   yielding   a   slightly   turbid    solution.     Lead 


44-8  ELECTRO-DEPOSITION    OF   METALS. 

acetate  is  employed  for  preparing  lead  baths  (Nobili's  rings) 
and  for  coloring  copper  and  brass. 

Recognition. — By  compounding  lead  acetate  solution  with 
potassium  chromate  solution,  a  heavy  yellow  precipitate  of  lead 
chromate  is  formed. 

75.  Sodium  citrate. — Colorless  crystals,  presenting  a  moist 
appearance,  which  are  readily  soluble  in  water;  the  solution 
should  show  a  neutral  reaction.  This  salt  is  employed  in  the 
preparation  of  the  platinum  bath  according  to  Bottger's  formula. 

B.  VARIOUS  APPARATUS  AND  INSTRUMENTS. 

Glass  balloons  and  flasks. — These  are  spheres  of  thin  blown 
glass,  Fig.  138,  with  necks  of  various  dimensions  in  length  and 
diameter.     They    are    employed    for    heating  acids, 
FIG.  138.      dissolving    metals,   and    a    great    many   other   uses. 
They  should  be  placed  upon  triangular  supports  of 
iron  and  at  a  certain  distance  from  the  fire,  from  the 
direct  action  of  which  they  are  to  be  protected  by 
the    intervention    of    a  piece    of  wire   gauze   or  its 
equivalent.     The  thinner  they  are  the  more  easily 
they  bear  sudden  changes   of  temperature.     They 
are   preferable  to  porcelain   evaporating   dishes  for 
dissolving  gold,  because  there  is  much  less  danger  of  losing  a 
part  of  the  product  by  spurting. 

Evaporating  dishes  or  capsules. — These  are  usually  vessels  of 
porcelain,  and  are  intended  to  bear  a  high  temperature.  The 
best  are  thin  and  uniformly  so.  Like  glass  flasks,  they  should 
be  supported  above  the  fire  upon  an  iron  stand  and  wire  gauze. 
As  far  as  practicable  they  should  be  gradually  heated  and 
cooled.  When  taken  from  the  fire  they  should  be  placed 
upon  rings  made  of  plaited  straw.  They  are  made  with  or 
without  lips,  and  some  have  a  socket  for  a  wooden  handle. 
Glass  evaporating  dishes  are  not  durable. 

Glass  jars. — These  are  glass  vessels,  generally  cylindrical, 
closed  at  one  end,  and  of  different  capacities. 

They  are  employed  for  small  gilding,  silvering,  and  electro- 


VARIOUS   APPARATUS    AND    INSTRUMENTS.  449 

plating  baths  in  the  cold.  They  are  handy  and  serviceable  for 
amateurs,  because  their  transparency  permits  the  progress  of 
the  operation  to  be  observed  at  all  times. 

Crucibles. — These   are   vessels,  the   shape   of  which   is  gen- 
erally an    inverted   truncated   cone,   Fig.    139,  the  smaller  end 
being  closed,  and  the  larger  open.     Sometimes  the 
opening  is  triangular.  FlG-  I39- 

Crucibles  are  made  of  many  kinds  of  materials : 
metals,  refractory  clay,  stoneware,  porcelain,  plum- 
bago or  graphite,  etc.  They  are  generally  provided 
with  a  cover  of  the  same  material,  and  are  raised 
above  the  grate  bars  of  the  furnace  by  means  of 
bricks  or  cylinders  of  clay.  Metallic  crucibles  may 
be  heated  rapidly,  but  the  others  require  to  have  their  temper- 
ature raised  gradually  and  carefully.  They  are  employed  for 
the  preparation  of  many  salts,  for  the  fusion  of  metals,  etc. 
Non-metallic  crucibles  are  rarely  used  for  more  than  one 
operation. 

Hydrometers. — These  are  glass  instruments  resembling  ther- 
mometers in  outward  appearance,  but  having  a  large  bulb  near 
the  bottom.  They  are  used  for  testing  the  specific  gravity  of 
liquids,  or,  in  other  words,  to  test  their  density  as  compared 
with  that  of  pure  water.  The  liquid  to  be  tested  may  be  placed 
in  a  narrow  glass  jar  together  with  the  hydrometer,  or'may  be 
contained  in  any  other  vessel.  The  instrument  floats  in  the 
liquid  to  be  tested,  with  its  bulb  below  the  surface  and  its  stem 
standing  above  the  surface.  This  stem  is  graded  into  degrees 
similar  to  that  of  a  thermometer,  and  shows  the  depth  of  the 
bulb  beneath  the  surface.  In  pure  water  the  bulb  sinks  down 
to  the  o°  mark,  or  to  i.ooo  as  marked  on  some  scales,  i.ooo 
being  taken  to  represent  the  density  of  water  at  a  temperature 
of  60°  F.  As  the  density  of  water  increases  by  the  addition  of 
salts  or  of  liquids  having  a  greater  density  than  water,  the  bulb 
is  forced  upwards,  and  the  scale  then  registers  so  many  degrees 
greater  density  than  water. 

Three    differently  graduated    hydrometers   are   in   use,   viz., 
29 


450 


ELECTRO- DEPOSITION    OF   METALS. 


hydrometers  graded  to  read  direct  the  specific  gravity  of  liquids 
in  comparison  with  that  of  water,  taking  this  as  represented  by 
i.ooo;  hydrometers  graded  by  a  scale  adopted  by  Mr.  W. 
Twaddell,  and  known  as  Twaddell's  hydrometers  ;  and  hydrom- 
eters graded  by  a  scale  adopted  by  M.  Baume,  and  named 
Baume's  hydrometers.  The  difference  between  the  three  grad- 
ings  is  shown  in  the  following  table: — 

Table  showing  readings  of  different  hydrometers. 


Specific  gravity. 

Baume. 

Twaddell. 

Specific  gravity. 

Baume. 

Twaddell. 

.817° 

40° 

_ 

1.250° 

_ 

500 

.827 

38 

— 

1.263 

30° 

•837 

36 

— 

1.300 

— 

60 

.847 

34 

— 

1.321 

35 

— 

.856 

32 

— 

1-350 

— 

7° 

.871 
.880 

30 
28 

z 

1.385 
1.400 

40 

80 

.892 

26 

— 

1.450 

— 

90 

.903 

24 

— 

1.454 

45 

— 

.915 

22 

— 

1.500 

— 

100 

.928 

20 

— 

1.532 

50 

— 

.942 

18 

— 

l-SS° 

no 

•955 

16 

— 

1.  600 

— 

120 

.970 

H 

— 

1.618 

55 

— 

.985 

12 

— 

1.650 

I30 

I.OOO 

o°  or  10 

0° 

1.700 

— 

I40 

1.036 

5 

— 

1.714 

60 

— 

1.050 

— 

10 

1.750 

— 

I|0 

J-°75 

10 

— 

i.  800 

— 

160 

.100 

— 

20 

1.823 

65 

— 

.116 

15 

— 

1.850 

170 

.150 

— 

3° 

1.900 

— 

1  80 

.161 

20 

1.946 

70 

— 

.200 

—     . 

40 

1.95° 

— 

190 

.210 

25 

It  will  be  seen  that  every  degree  Twaddell  represents  0.005° 
in  the  specific  gravity  hydrometer,  and  every  10°  represents 
0.050°.  To  convert  degrees  Baume  into  readings  showing 
direct  specific  gravity,  subtract  the  readings  on  Baume's  scale 
from  the  number  144,  and  divide  this  by  the  difference.  For 

example,  144  —  66  =  1^4  =  1.846°,  the  specific   gravity  of  a 

78 
liquid  registering  66°  on  a  Baume  hydrometer.     Baume  has 


VARIOUS   APPARATUS    AND    INSTRUMENTS. 


451 


FIG.  140. 


one  hydrometer  for  liquids  lighter  than  water  (the  readings  of 
which  are  given  in  the  first  16  sets  of  figures  in  the  foregoing 
table),  and  one  for  liquids  heavier  than  water. 

Filters. — Filtering  a  solution,  a  bath,  or  any  other  liquor, 
consists  in  causing  it  to  pass  through  a  permeable  substance, 
the  pores  or  meshes  of  which  are  sufficiently 
closed  to  retain  all  the  undissolved  substances, 
which  are  thus  separated  from  the  liquid  part. 

Filters  are  of  very  different  materials  and 
shapes.  Cloth,  muslin,  etc.,  are  coarse  filters 
or  strainers,  made  in  the  form  of  pockets. 
Their  filtering  power  is  considerably  improved 
by  covering  them  with  a  layer  of  sand,  wool, 
boneblack,  etc.  These  latter  substances  them- 
selves, properly  supported,  will  act  as  filters. 

Felted  wool  (generally  rabbit's  hair)  is  made  in  the  shape  of 
a  conical  pocket  (Fig.  140),  but  is  suited  only  for  neutral  sub- 
stances. Alkalies  destroy  it  rapidly. 

Concentrated    acids    are     filtered    through    amianthus,    or 
asbestos,  compressed  in  the  neck  of  a  glass  funnel 
upon  broken  fragments  of  glass. 

The  most  useful  filtering  material,  however,  is 
unsized  paper.     This  filter  (Fig.  141)  is  prepared 
by  folding  diagonally  a  square  piece  of  porous 
paper,    which    thus    prepared    forms    a    triangle. 
This  is  again  folded  in  half.     Then,  beginning  at 
one  edge,  smaller  folds  are  made  alternately  to  the  right  and 
to  the  left,  but  all  converging  towards  the   point,  like  a  fan. 
The  filter  is  now  partially  opened,  trimmed  on  top,  and  intro- 
duced into  the  funnel,  care  being  had  that  all  the 
projecting  edges  rest  against  it. 

If  it  be  feared  that  the  filter  will  not  resist  the 
weight  of  the  liquid,  the  point  is  twisted  to  the 
left  or  to  the  right,  and  while  it  is  still  held  be- 
tween two  fingers  of  the  left  hand,  the  whole  filter 
is  inverted,  so  that  the  inward  folds  become  the  outward 


141. 


Fir,.  142. 


452 


ELECTRO-DEPOSITION    OF   METALS. 


ones.  A  filter  with  such  a  rounded  point  is  better  supported 
in  the  funnel,  and  filters  more  rapidly. 

This  method  is  preferable  for  rapid  filtration ;  but  if  it  is  de- 
sired to  recover  precipitates,  the  filter  represented  by  Fig.  142 
is  more  suitable.  A  circular  sheet  of  paper  is  twice  doubled 
up,  and  by  carefully  opening  it  three  thicknesses  of  paper  are 
laid  on  one  side,  leaving  one  single  thickness  on  the  other  side. 

Siphons. — The  most  simple  and  handy  siphon,  in  many 
cases,  is  a  piece  of  lead  pipe  bent  so  as  to  have  two  unequal 
branches,  the  smaller  of  which  plunges  into  the  liquid  to  be 
drawn  oft".  A  section  of  India-rubber  tube  may  be  employed 
for  similar  purposes. 

But  as  these  materials  may  be  chemically  acted  upon  by 
various  solutions,  glass  siphons  are  used,  with  or  without  a 
suction  tube  (Figs.  143  and  144). 


FIG.  143. 


FIG.  144. 


For  siphoning  corrosive  solutions  which  cannot  be  touched 
with  the  fingers,  a  siphon  with  a  suction  tube  is  used  (Fig. 
143).  The  shorter  leg  is  plunged  into  the  liquid  and  the 
longer  one  closed  with  the  finger  or  an  India-rubber  pad 
pressed  against  it;  then,  with  the  mouth,  suction  should  be 


VARIOUS   APPARATUS   AND    INSTRUMENTS.  453 

carefully  applied  at  the  lateral  suction  tube  until  the  liquid 
fills  the  longer  leg. 

If  there  be  any  danger  of  inhaling  a  poisonous  vapor,  the 
action  of  the  mouth  may  be  replaced  by  an  India-rubber  ball 
fastened  to  the  suction  tube.  The  longer  branch  of  the  siphon 
is  closed  as  before,  and  the  ball  compressed  in  order  to  remove 
the  air.  By  its  elasticity  the  ball  resumes  its  former  volume, 
thus  producing  a  suction  which  starts  the  siphon  in  action. 

Stirring  rods. — These  are  rods  made  of  various  materials, 
and  are  employed  for  mixing  together  liquids  or  pastes,  or 
liquids  and  pastes,  or  solids  with  liquids,  or  various  solids  in 
the  dry  state.  Their  length  and  thickness  should  be  suited  to 
the  volumes  to  be  mixed. 

Suitable  stirring  rods  are  those  which  have  no  chemical 
action  upon  the  substances  with  which  they  are  brought  in 
contact;  neither  should  they  become  impregnated  with  them. 
Rods  of  glass,  stoneware,  or  porcelain  are  decidedly  the  best. 
Wood  and  most  metals  should  be  avoided,  because  the  former 
is  absorbent  and  the  latter  are  corroded  and  easily  oxidized. 

The  operator  should  always  have  near  at  hand  a  complete 
assortment  of  glass  stirrers  of  various  sizes,  and  with  fused  or 
rounded  ends,  in  order  not  to  scratch  the  vessels  in  which  he 
operates. 


APPENDIX. 


FIG.  145. 


CHECK    VOLTMETER. 

UNDER  "  Electro-Plating  Arrangements  in  Particular,"  p.  89, 
et  seq.,  reference  has  been  made  to  various  styles  of  voltmeters. 

In  addition  attention  may  be 
called  here  to  the  check  volt- 
meter, Fig.  145,  manufactured 
by  the  Hanson  &  Van  Winkle 
Co.,  of  Newark,  N.  J.,  and  de- 
signed for  small  plants  or  for 
connection  with  every  tank  in 
larger  establishments. 

The  cost  of  the  large  volt- 
meters is  an  obstacle  to  their 
general  use,  except  in  the  main 
circuit,  where  they  are  usually 
placed  at  a  distance  from  the 
tanks,  and  do  not  show  the 
variation  in  voltage  between  the 
dynamo  and  tanks  caused  by 
resistance  of  the  conductors. 

The  check  voltmeter  can  be 
connected  with  each  tank,  and 
is  of  great  advantage  to  the 
plater  who  is  operating  baths 
requiring  different  voltages,  for 
by  touching  the  'button  of  the 
switch  the  tension  of  current  at  each  tank  can  be  instantly  de- 
termined. The  instrument  is  calibrated  from  a  standard  volt- 
meter and  is  reliable.  It  cannot  be  left  in  circuit,  and  for  this 

(454) 


UNIVERSITY 


APPENDIX. 


455 


reason  a  switch  is  provided.     The  price  of  the  instrument  is 
$2.50. 

The  Bossard  Mechano- Electroplating  Tanks. 
These  tanks  are   patented  devices  in  which  the  work  to  be 
plated  is  automatically  drawn  through  the  bath  at  a  controllable 
rate  of  speed.     There  are  two  styles  of  these  devices,  namely, 
the  "  long  tank"  and  the  "  circular  tank" 

FIG.  146. 


The  long  tank,  Figs.  146  and  147,  is  made  of  wood  or  plate 
steel.  Two  rigid  bridges  span  the  tank  longitudinally,  their  top 
faces  being  mounted  their  entire  length  by  a  metal  strip,  which 
can  be  directly  connected  to  the  cathode  rheophore  of  dynamo. 
Preferably  the  cathode  element  is  brought  into  the  apparatus 
by  a  connection  to  the  copper  strips,  which  are  found  extend- 
ing on  each  side  at  bottom  of  bridge.  Upon  each  of  the 
bridges  is  traveling  an  endless  chain  encircling  the  tank  longi- 
tudinally. Sprocket  wheels  upon  a  shaft  at  one  end  of  tank, 
which  are  driven  by  a  simple  and  effective  mechanical  move- 
ment consisting  of  a  ratchet  wheel,  pallet  upon  rocker  arm, 
pitman  and  slide  crank,  give  motion  to  the  chains.  An  adjust- 
able wrist-pin  on  slide-crank,  holding  one  end  of  pitman,  is  the 
means  whereby  the  shortening  and  lengthening  of  stroke  of  the 
latter,  and  with  it  the  path  of  pallet  on  ratchet-wheel,  and  con- 


456 


APPENDIX. 


sequently  the  speed  of  sprocket-wheel  shaft,  is  fixed.  The 
speed  of  the  chain  is  determined  by  the  time  it  is  desired  to 
give  the  work  to  be  plated  in  the  bath.  The  work  is  hung  into 
the  bath  on  hooks  or  frames  at  one  end  of  tank,  suspended 
from  each  side  of  bridge.  Engaging  in  the  chain  it  moves  with 
the  latter,  and  when  it  has  reached  the  other  end  in  its  travel 
through  the  bath,  is  removed  as  sufficiently  plated.  Electric 
contact  is  made,  either  at  juncture  of  hook  with  metal  strip  on 
top  face  of  bridge,  or  hook  and  copper  strip  on  side  of  bridge,  or 
at  both  points.  Along  the  sides  and  through  the  middle  of  the 
bath  are  three  rows  of  anodes.  For  the  purpose  of  controlling 
the  anode  surface  in  the  bath,  the  anodes  are  suspended  in 
small  numbers,  from  short  sections  of  rod,  which  are  individ- 
ually and  movably  connected  by  switch  to  the  feed-rods 


FIG.  147. 


charged  with  the  anode  element  of  dynamo.  This  arrangement 
enables  the  operator  to  use  such  amount  of  anode  surface  in  the 
bath  as  will  insure  good  work. 

In  the  manipulation  of  this  tank  it  is  the  operator's  task  to 
fix  the  time  the  work  is  to  take  in  its  travel  through  the  bath, 
adjust  the  speed  of  chain  accordingly,  regulate  at  the  switch- 
board the  electric  current  going  into  the  bath,  pass  the  work 
through  lye  and  cleansing  dips,  suspend  it  in  the  bath,  the 
hooks  holding  same  to  engage  in  the  moving  chain.  The 
work  requires  no  care  while  going  through  the  bath.  Arriv- 


APPENDIX. 


457 


ing  at  the  other  end  it  is  taken  out  by  a  workman,  whose 
further  duty  it  is  to  pass  the  work  through  hot  water  and  dry 
it  off  in  the  usual  manner. 

The  long  tank  is  highly  spoken  of  by  manufacturers  of  hard- 
ware for  the  deposition  of  copper,  brass  and  bronze  on  steel 
goods  and  gray-iron  castings,  among  its  users  being  The  Yale 
and  Towne  Manufacturing  Co.,  Stamford,  Conn.,  The  Russell 
and  Erwin  Manufacturing  Co.,  New  Britain,  Conn.,  and  The 
Stanley  Works,  New  Britain,  Conn. 

The   circular  tank,  Figs.    148   to    150,  consists  chiefly   of   a 

FIG.  148. 


large  wooden  tub  in  which  a  circular  carrier  is  caused  to  re- 
volve upon  a  horizontal  plane.  Fig.  148  shows  an  exterior 
view  of  the  tank,  Fig.  149  a  plan  of  the  tank  and  carrier,  and 
Fig.  150  section  and  partly  front  elevation  of  the  tank,  carrier 
and  machinery.  A  peculiarity  of  the  wooden  tub  is  its  open 
central  space  which  gives  it  the  quality  of  a  circular  trough. 
In  the  construction  of  the  tank  the  size  and  shape  of  the  work 
to  be  plated  determine  the  dimensions  of  this  trough.  The 


458 


APPENDIX. 


quantity  of  work  decides  the  general  dimensions  of  the  tank 
and  of  the  open  central  space. 

The  carrier  is  constructed  to  hold  two  rows  of  work  of  con- 
siderable lineal  capacity  and  to  move  above  bath  and  tank.  It 
is  mounted  upon  a  perpendicular  shaft,  and  this  by  means  of  a 
worm  gear  at  lower  end  and  properly  supported  within  the 
open  central  space  is  revolved,  and  its  speed  adjusted  by  a 

FIG.  149. 


mechanical  contrivance  similar  to  the  one  applied  for  the  same 
purpose  to  the  long  tank. 

In  this  device  the  general  principle  is  recognized  which 
underlies  the  long  tank,  but  somewhat  different  results  attend 
its  operation,  attributable  to  its  shape.  The  arrangement  for 
controlling  the  anode  surface  in  the  bath  is  the  same,  the  deri- 
vation of  the  frictional  electric  contact  between  work  and 
cathode  bar  is  similar;  but  on  account  of  its  circular  shape 


APPENDIX. 


459 


and  movement  the  work,  suspended  from  the  carrier  as  it 
passes  through  the  bath  in  its  circular  course,  returns  to  its 
original  starting  point  when  completing  its  revolution.  This 
enables  the  operator  to  occupy  one  position,  in  which  he  con- 
tinuously supplies  the  bath  with  work  and  withdraws  the  same 
as  it  returns  to  him  plated.  The  walking  forward  and  back  in 

FIG.  150. 


SECTION  AND  PARTLY  FRONT  ELEVATION  OF  CIRCULAR  TANK,  CARRIER  AND  MACHINERY. 

the  course  of  attention  the  old-style  tanks  require,  is  thereby 
entirely  saved,  and  a  great  point  of  economy  gained.  The 
cleansing  tanks,  hot  and  cold  water,  pickles  and  dips  are  placed 
near  the  operator's  position  at  the  circular  tank,  which  at  once 
simplifies  and  brings  closer  together  the  general  operations  of 
the  plating  room,  saves  floor  space,  and  adds  to  the  facilities  of 
keeping  the  room  clean  and  dry.  It  times  the  operation  of 


UNIVERSITY 


APPENDIX . 

plating    in   the    bath  automatically  and    insures  uniformity  of 
product. 

The  advantages  claimed  by  the  inventor  from  the  shape  and 
general  construction  of  these  devices  are  as  follows : 

1.  The  work  to  be  plated,  as  it  is  drawn  through  the  bath, 
continuously    stirs    the    latter,    thereby    keeping    it    in    active 
chemical   condition.     The   hydrogen    bubbles    formed'  on   the 
work  are  constantly  dislodged,  the  result  being  a  rapid,  smooth, 
and  homogeneous  deposit. 

2.  The  frictional  contact  derived    from   the  bearing   of  the 
hooks  carrying  the  work  into  the  bath  against  the  cathode  bar, 
insures  a  keen,  never  fading,  electric  action  to  enter  the  bath. 
The  contact  points  are  always  clean  and  sure. 

3.  The  movement  through  the  bath  passes  the  work  in  con- 
stantly changing  positions  before  the  anodes  while  undergoing 
the  process  of  deposition. 

4.  To   increase    the   movement  of    the  work  and    vary    the 
nature  of  the  motion  during  its  travel  through  the  bath,  small 
deflecting  devices  are  introduced  at  desired  distances  along  and 
upon  the  cathode  bars,  and  for  special  work,  revolving  hooks 
have  been  used  to  great  advantage. 

5.  The  proximity  of  the  work  to  the  anode  in  the  plating 
bath  is  well  known  to  cause  conditions  favorable  or  unfavorable 
to  the  formation  of  a  good  deposit.     Experiments  have  plainly 
shown  and  the  daily  application  of  these  devices  proves  that  the 
distance  between  the  work  and  the  anode  can  be  considerably 
reduced   and    the   intensity  of    the   current   increased   without 
danger  of  burning  the  work  when  the  latter  is  gently  moved. 
By  reducing  distance  between  anode  and  cathode,  the  resist- 
ance upon  the  dynamo  is  accordingly  diminished,  and  this  con- 
dition is  very  desirable  in  nickel  and  other  solutions  which  are 
of  a  neutral  and  non-conducting  nature. 

In  may  finally  be  observed  that  while  in  the  electro-deposi- 
tion of  metals  the  moving  of  the  work  in  the  bath  is  not  new, 
and  its  effects  are  well  known  and  appreciated,  the  manner  in 
which  the  movement  is  produced  in  these  devices  and  the  idea 


APPENDIX. 


461 


of  having  the  work  enter  the  bath,  pass  through  the  same,  and 
approach  a  desired  point  for  removal  at  an  adjustable  rate  of 
speed,  are  both  new  and  novel,  and  the  results,  as  a  conse- 
quence to  construction  and  conditions  thereby  created  in  the 
bath,  can  be  readily  understood. 

The  Bossard  Mechano-Electroplating  Tanks  are  manufac- 
tured tiy  the  Schreiber  &  Conchar  Manufacturing  Co.,  of 
Dubuque,  Iowa. 

USEFUL  TABLES. 

Table  of  elements  with  their  symbols,  atomic  weights,  and 
specific  gravities. 


Name. 

Sym- 
bol. 

Atomic 
weight. 

Specific 
gravity. 

N-<-      :tT 

Atomic 
weight. 

Specific- 
gravity. 

Al 
Sb 
As 
Ba 
Be 
Bi 
B 
Br 
Cd 
Cs 
Ca 
C 
Ce 
Cl 
Cr 
Co 
Cu 
D 
E 
F 
Au 
H 
In 
I 
Ir 
Fe 
La 
Pb 
Li 
Mg 
Mn 
Hg 

27.4 

122 

75 
137 
9-3 
208 
ii 
80 

I  12 

133 
40 
12 

92 

35-5 

58.8 
634 
95 

112.6 

19 
197 

75.6 
127 
197.4 
56 
92 
207 

7 
24 

55 
200 

2.67 
6.72 

5-63 
4.00 

2.IO 

9-799 

2.68 
2.97 
8.67 

3.10 
3-50 

245 

6.81 
8.50 
8.88 

— 

J9-5° 
0.069 

4.98 
21.15 
7.70 

11.38 

0.59 
1.74 
8.co 
'3-59 

Molybdenum   .  .  . 
Nickel 

Mo 

Ni 
Nb 
N 
Os 
O 
Pd 
P 
Pt 
K 
Rh 
Rb 
Ru 
Se 
Si 
Ag 
Na 
Sr 
S 
Ta 
Te 
Tl 
Th 
Sn 
li 
W 
U 
V 
Y 
Zn 
Zr 

96 
58 

94 
14 
199-4 
16 
106.6 

31 

197.4 

39-1 
104.4 

854 
1044 

794 
28 
108 
23 
87.5 
32 
182 
128 
204 
231 
118 

£ 

120 

5!-3 
68 

65 
89.6 

8.60 
8.6 
6.67 
0.972 
21.3 
i.  088 
1  1.8 
1.84 
21.15 
8.865 

I2.IO 
I.50 
1140 
4.28 
2.49 
10.50 
0.972 

2-54 
2.045 
10.78 
6.18 

11.86 
7.70 
7.29 

5-30 
19.10 
1840 
5-50 

7.2 
4.20 

Arsenic  

Oxvcren 

Palladium  

Phosphorus    .... 
Platinum    

Cadmium   •....• 

Ruthenium  

Chlorine  

Chromium    
Cobalt  

Silver    

Didymium    

Strontium  

Gold   

Hydrogen    

Thallium    

Tin 

Lanthanum    .... 
Lead 

Vanadium    
Yttrium 

Magnesium    
Manganese  

462  APPENDIX. 

Table  of  chemical  and  electro-  chemical  equivalents. 


Name  of  substance. 

Sym- 
bol. 

Specific 
gravity. 

Chemical 
equiva- 
lent. 

Electro- 
chemical equi- 
valent. 
Milligrammes. 

Weights 
decomposed 
by  i  ampere 
in  I  hour. 
In  grammes. 

Hydrogen  

H 

j 

o  01036 

O  O37C 

Aluminium    

Al 

26 

11  7 

O  I42CO 

"•HJ/3 

O  r  i  -27 

Sb 

68 

122 

I  26880 

^•D1  Jl 

A    C7CQ 

As 

7C 

o  78000 

4o/y 

2  8l2C 

Cobalt   

Co 

j'/ 

8  7 

Jj 
2Q  £ 

o  30680 

I   IO62 

Copper  

Cu 

88 

11  8 

O  77C7O 

I   IQ2£ 

Gold  

Au 

IQ  2 

08  ^ 

I  O223O 

3  6862 

Fe 

28 

O  2Q  I  2O 

Lea(j    

Pb 

•D 
117 

IO7  £ 

I  07640 

-7  ggl2 

Nickel    

Ni 

86 

2Q  C 

o  30680 

I   IO62 

Pt 

98  6 

Arr 

TQ  r 

1  08 

112  34O 

o-uy/.) 

Tin  

Sn 

1UO 
1  "? 

•32  7 

o  34010 

i  2262 

Zn 

i'J 
72 

O-''/ 
en 

o  61  360 

2  212*5 

•* 

j? 

With  the  assistance  of  this  table  it  can  be  calculated  how 
long  a  measured  surface  has  to  remain  in  the  bath  in  order  to 
acquire  a  deposit  of  determined  weight  with  the  most  suitable 
current  density.  Suppose  the  time  is  to  be  determined  which 
a  square  decimetre  of  surface  has  to  remain  in  the  nickel  bath 
in  order  to  acquire  a  deposit  of  y1^  millimetre  thick  with  a  cur- 
rent density  of  0.5  ampere.  First  calculate  the  weight  of  the 
deposit  by  multiplying  the  surface  in  square  millimetres  with 
the  thickness  and  specific  gravity.  One  square  decimetre  is 
equal  to  10,000  square  millimetres,  which,  multiplied  by  T^  milli- 
metre, gives  as  a  product  1000,  which,  multiplied  by  the 
specific  gravity  of  nickel — 8.6 — gives  8600  milligrammes  =  8.6 
grammes.  Since,  for  the  regular  deposit  per  square  decimetre, 
a  current  density  of  0.5  ampere  is  required,  and  i  ampere  de- 
posits, according  to  the  above  table,  1.1062  grammes  in  i  hour, 
y2  ampere  deposits  0.5331  gramme  in  i  hour,  and,  therefore, 
about  1 6  hours  will  be  required  for  the  deposition  of  8.6 
grammes. 

According  to  this  example,  the  time,  for  instance,  can  also  be 


APPENDIX. 


463 


calculated  which  one,  two,  or  more  dozen  of  knives  and  forks 
or  spoons,  which  are  to  have  a  deposit  of  silver  of  a  determined 
weight,  must  remain  in  the  bath  when  the  current  density  is 
known.  Suppose  50  grammes  of  silver  are  to  be  deposited 
upon  i  dozen  of  spoons,  and  the  most  suitable  current  density 
is  0.2  ampere  per  square  decimetre ;  if  the  surface  of  I  spoon 
represents  i.io  square  decimetres,  the  surface  of  I  dozen 
spoons  of  equal  size  is  13.2  square  decimetres.  Hence,  they 
require  13.2  x  0.2  =  2.64  amperes;  now,  since  I  ampere  de- 
posits in  one  hour  4.05  grammes  of  silver,  2.64  amperes  deposit 
in  the  same  time  10.7  grammes  of  silver,  and  with  this  current 
the  dozen  spoons  must  remain  about  4^  hours  in  the  bath  for 
the  deposition  of  50  grammes  of  silver  upon  this  surface. 

Table  showing  the  value  of  equal  current  volumes  as  expressed  in 
amperes  per  square  decimetre,  per  square  foot,  and  per  square 
inch  of  electrode  surface. 


Amperes 
per  square 
decimetre. 

V)    &> 

%  5 

-<L>     3 

o,cr 
£      .J 

fsJ 

II 
Ifj 

Isj 

Amperes 
per  square 
decimetre. 

l*^ 

<0 

11 

if 

|:-s 
i  ^-a 

Amperes 
per  square 
decimetre. 

S  £ 

¥   rt 

0    X 

|^ 

^g§ 
II    ^ 

=  Ampees 
per  square 
inch. 

0.05 

0.46 

0.0032 

0.8 

743 

0.0516 

6.20 

57-6 

0.4 

0.054 

°-5 

0.0035 

0.86 

8 

°-°555 

6.46 

60 

0.4167 

0.077 

0.72 

0.005 

0.9 

8.36 

0.0581 

7 

65.0 

0.4516 

O.I 

o.93 

0.0064 

0-93 

8.64 

0.06 

7-53 

70 

0.4861 

O.I  I 

i 

0.0069 

0.97 

9 

0.0625 

7-75 

72.0 

°-5 

0.15 

1.44 

O.OI 

9.29 

0.0645 

8 

74-3 

0.5161 

0.2 

1.86 

0.0129 

i.  08 

10 

00694 

8.61 

80 

0-5555 

0.22 

2 

0.0139 

1.09 

10.28 

0.07 

9 

83.6 

0.5806 

0-3 

2.79 

0.0193 

1.24 

11.52 

0.08 

9-30 

86.4    |  0.6 

0.31 

2.88 

0.02 

i-39 

12.96 

0.09 

9.69 

90         0.6250 

0.32 

3 

O.O2O8 

'•55 

14.4 

C.I 

10. 

92.9 

0.6452 

0.4 

3-71 

0.0258 

2 

1  8.6 

0.1290 

10.76               100         :    0.6944 

0-43 

4 

0.0278 

2.15 

20 

0.1389 

10.85 

100.8      0.7 

0.46 

o-5 

4-32 
4.64 

0.03 
0.0323 

3 
3.10 

27.9 
28.8 

0.1935 

O.2 

I2.4O 
13-95 

115.2 

129.6 

0.8 

0.9 

0-54 

5 

0.0348 

3-23 

30 

0.2083 

IS-S° 

144.0 

1 

0.6 

5-57 

0.0387 

4 

37-i 

0.2581 

20                      185.8 

1.2903 

0.62 

5.76 

0.04 

4-30 

40 

0.2778 

21.53               2CO              1.3889 

0.65 

6 

0.0417 

4.60 

43-2 

0-3 

3°               278.7    !   1.9355 

0.7 

6.50 

0.0452 

5 

46.4 

0.3226 

31.0            288 

2 

o-75 

7 

0.0486 

5.38 

50 

0.3478 

32.3            300 

2.0833 

0.77 

7.20 

0.05 

6 

55-7 

0.3871 

46.5 

432.0 

3 

464 


APPENDIX. 


By  this  table  the  current  density  may  be  expressed  in 
amperes  per  square  decimetre,  square  foot,  or  square  inch,  any 
of  them  being  given.  Thus  a  current  of  I  ampere  per  square 
decimetre  has  the  same  electrolytic  value  as  one  of  9.29 
amperes  per  square  foot,  or  0.0645  Per  square  inch.  To  find 
the  value  of  intermediate  numbers,  not  shown  above,  add  to- 
gether the  various  numbers  representing  the  hundreds,  tens, 
units,  and  decimals  of  the  given  quantity.  Thus  27.5  amperes 
per  square  decimetre  (=20+7+5)  are  equivalent  to  185.8  + 
65+4.64=255.44  amperes  per  square  foot,  or  1.290340.4516+ 
0.0323  =  1.7742  amperes  per  square  inch. 

Table  showing  the  specific  electrical  resistances*  of  different  sul- 
phuric acid  solutions  at  various  temperatures  (Fleeming 
Jen  kin). 


Specific 

Temperatures  (Fahrenheit). 

gravity  of 

acid. 

32° 

39.2° 

46.4° 

53.6° 

60.8° 

68° 

75.2° 

82.4° 

.10 

•37 

1.17 

1.04 

0.92 

0.84 

0.79 

0.74 

0.71 

.20 

•33 

i.  ii 

o.93 

0.79 

0.67 

o-57 

0.49 

0.41 

•25 

•31 

1.09 

0.90 

0.74 

0.62 

0.51 

0-43 

0.36 

•30 

.36 

i.i3 

0.94 

0.79 

0.66 

0.56 

o.47 

0-39 

.40 

.69 

1.47 

1.30 

1.16 

1.05 

0.96 

0.89 

0.84 

•5° 

2.74 

2.41 

2.13 

1.89 

1.72 

1.61 

1.32 

1.43 

.60 

4-32 

4.16 

3-62 

3-" 

2-75 

2.46 

2.21 

2.02 

.70 

9.41 

7.67 

6.25 

5-i2 

4.23 

3-57 

3.07 

2.71 

Table  showing  the  specific  electrical  resistances*  of  different  copper 
sulphate  solutions  at  various  temperatures  {Fleeming  Jenkin). 


No.  of  parts  of 
copper  sulphate 
dissolved  in  100 
parts  of  water. 

Temperatures  (Fahrenheit). 

57.2° 

60.8C 

64.4° 

68° 

75.2° 

82.4C 

86° 

8 

12 

16 

20 
24 
28 

45-7 
36.3 
31.2 
28.5 
26.9 
24.7 

43-7 
34-9 
30.0 

27-5 
25.9 
234 

41.9 

33-5 
28.9 
26.5 
24.8 

22.1 

40.2 
32.2 
27.9 
25.6 
23-9 

21.0 

37-i 
29.9 
26.1 
24.1 

22.2 

18.8 

34.2 
27.9 
24.6 
22.7 
20.7 
16.9 

32.9 
27.0 
24.0 

22,2 
20.0 

16.0 

*  By  the  term  "specific  resistance,"  in  the  above  tables,  is  meant  the  absolute  re- 
sistance in  ohms  of  a  column  of  the  liquid  I  square  centimetre  in  cross-section  and  I 
centimetre  long;  in  other  words,  it  is  the  resistance  of  a  cubic  centimetre  of  the 
liquid.  The  diminution  of  resistance  accompanying  a  rise  of  temperature  should  be 
especially  marked. 


APPENDIX.  465 

Table  of  the  electro-motive  force  of  elements. 


Name  of  element. 

Constitution. 

Electro- 
motive force 
in  volts. 

Authority. 

Amalgamated  zinc  and  cop- 

f 0.886 

Clark  and  Sabine 

Smee  

per  in  dilute  sulphuric  acid 
(1:12). 

Amalgamated    zinc    in    sul- 

\ 0.861 
(0.719 

C  I  008 

Sprague. 
De  la  Rive. 

Clark  and  Sabine 

• 
Daniell 

phuric      acid;       platinized 
silver,  or  platinum   in  sul- 
phuric acid  (i  :  12). 

1  !-I07 

1  0.541 
[1.192 

Sprague. 
De  la  Rive. 
Naclari. 

Clark  and  Sabine 

do   

phuric    acid    (1:4);     cop- 
per  in    saturated    solution 
of  copper  sulphate. 

Zinc  in  dilute  sulphuric  acid 

i.u/y 

do. 

do. 
do. 

f  O  Q?8 

Sprague. 
De  la  Rive. 
Naclari. 

Clark  and  Sabine 

Leclanche    

(i  :  12)  ;   copper  as  above. 
Zinc  in  sal  ammoniac  carbon 

1  0.98 

{I  4.81 

Du  Moncel. 

do   

with   manganese    peroxide 
in  sal  ammoniac. 

Zinc  in  solution  of  common 

1.561 

1.942 
1.259 

(  I  AQI 

Sprague. 
De  la  Rive. 
Beetz. 

Marie  Davy  

salt;   carbon   with    manga- 
nese peroxide   in   common 
salt  solution. 

i^yj 
1  1.360 

1  1-34 

f  I  C24. 

Naclari. 
Du  Moncel. 

(i  :  12)  ;   carbon  in  mercu- 
rous  sulphate. 

At3^4 
i    1-542 
1    1.482 
[1.440 

Sprague. 
Naclari. 
Du  Moncel. 

do   

(i  :  12);   platinum  in  fum- 
ing nitric  acid. 

1.956 
f  I   C2A 

Clark  and  Sabine. 

nitric  acid  of  1.38  sp.  gr. 

i    i.^q. 
I  1-542 

f  I  Q6A 

Sprague. 

do   

fuming  nitric  acid. 

I  !-95 

{i  888 

Du  Moncel. 
Clark  and  Sabine 

do  

nitric  acid  of  1.38  sp.  gr. 

1.941 
1.880 

f  2  O28 

Beetz. 
Naclari. 

Grenet    

chromate  of  potassium. 

\    I-905 
(  2.120 

I  82C 

Sprague. 
Naclari. 

mate  of  potassium. 

&«o«5 

30 


466  APPENDIX. 

Table  showing  the  solubility  of  various  substances. 


Substances  of  which  I  part  is  soluble 

In  water 

In  alcohol  of 
59°  F. 

of  59°  F. 

of  212°  F. 

6.5 
4.0 
0-75 

5-P 

0.6 

0.8 

i-5 

7000 

2.0 

3-0 
0.9 

o-5 

readily  soluble 

10 

3-0 

sparingly 
soluble 
0.8 

I.O 

2.O 

soluble 

2.8 

4.0 
4.0 
0-3 

2.0 

0-3 
decomposes 
0.6 

i-3 

very  soluble 

M 

0-3 

soluble 
very  soluble 

2.O 

very  soluble 
« 

readily  soluble 

1.2 

1.4 

sparingly 
soluble 
very  soluble 

0-3 

°-5 

soluble 

2-5 

1.0 
I.O 

very  soluble 

I.O 

insoluble, 
soluble, 
soluble, 
insoluble, 
soluble, 
soluble, 
insoluble, 
readily  soluble, 
soluble, 
insoluble, 
insoluble, 
soluble, 
soluble. 

insoluble, 
sparingly 
soluble. 

"       sulphate  

Potash  

"          dichromate    (red  chromate 

i  part  at  a 
boiling  heat, 
insoluble, 
insoluble. 

60 

insoluble, 
insoluble. 
i 
insoluble. 

Soda                                                        r  ., 

"        chloride  *  

Table  Showing  the  Composition  of  the  Most  Usual  Alloys  and 

Solders. 

Alloys  are  combinations  or  mixtures,  effected  by  the  fusion 
of  two  or  more  different  metals  in  definite  proportions.  The 
electro-plater  employs  them  so  constantly  that  it  is  important 
that  he  be  acquainted  with  the  compositions  of  the  most  usual 
alloys,  and  that  he  learn  the  preparation  of  several  of  them, 
which,  like  the  fusible  alloys  of  Darcet,  will  often  be  serviceable. 

It  is,  of  course,  possible  to  vary  ad  infinitum  the  mixtures 
and  the  proportions  of  the  component  metals  given  in  the  fol- 


APPENDIX. 


467 


lowing  table,  and  thus  to  arrive  at  an  unlimited  number  of 
alloys  which,  on  account  of  slight  differences  of  color,  ductility, 
sonorousness,  etc.,  have  received  a  great  variety  of  names.* 

I.  Alloys. 


<u 

a 

3 

<J 

d 

N 

.S 

-d 

5 

TJ 

-3 

£ 

Bismuth. 

Antimony. 

Arsenic. 

| 

PARTS. 

Armenian   elastic  

574 

70 
66 
60 

75 
4 

10 

80 
78 
42 

21 

100 
100 

90 

93 
84 
84 
82 
80 

5° 
53 

4 
55 
11.9 

ICO 

86.6 

IOO 

80 

76 

88 
84 

25 

30 
32 
40 

25 

6 

ii 

10.5 

3-5 
31-25 

3-5 
i 

J7 
24.9 

12 

12.6 

20 

24 

12 

16 

7°-5 

22 
20 
22 

58 

25 
2O 

25 
10 

16 

4 
18 
8 
4 
3 

2 

2 
1.2 

2.4 

50 

2 

4 
5 
3 

O.2 
1.2 

13 

i  — 

25-5 
62 

— 

9 

Brass  for  articles  worked  with  the 

"      for  sheet  

Britannia  •  

<( 

"       for  clocks 

"       for  medals  

"       for  large  ordnance  

"       for  small  ordnance  

— 

— 

— 

— 

— 

«                « 

«               « 

4 
'5-75 
3 

23 

8 
8 
5 

— 

i 

3 

Darcet's  fusible  alloy  

«             «         « 

«(             «         « 

«          « 

««          « 

«          « 

Potin  (French  yellow  brass)     .... 

Talmi  gold  

Telescope  mirrors  (reflectors)  
Tombac  

«       pale  

«        red  

*  For  a  full  description  of  alloys  and  amalgams  see  "The  Metallic  Alloys,"  edited 
by  W.  T.  Brannt.     Philadelphia.     Henry  Carey  Baird  &  Co.     1896. 


468 


APPENDIX. 


2.  Solders. 

a.  Soft  Solder. 


Tin. 

Lead. 

Tin. 

Lead. 

Melts 

Melts 

PARTS. 

at  degrees  F. 

PARTS. 

at  degrees  F. 

25 

558° 

l& 

334° 

10 

541 

2 

340 

5 

5" 

3 

356 

3 

482 

4 

2 

441 

5 

378 

I 

37° 

6 

38i 

b.  Hard  Solder. 


Brass. 

Zinc. 

Tin. 

PARTS. 

gc  42 

12  ?8 

«               « 

_ 

(( 

j 

2 

u 

Half  white  

12 

/Id. 

2O 

2 

"White  

4O 

2 

g 

u 

22 

2 

« 

18 

12 

78  2S 

17  2C 

ou 

•/••3 

c.  Silver  Solder. 


Silver. 

Copper. 

Brass. 

Tin. 

Zinc. 

PARTS. 

A.O 

JO 

AQ 

AQ 

10 

•72 

J" 

20 

32 

Silver  solder  for  steel  

3 

* 

APPENDIX, 
d.  Gold  Solder. 


469 


Gold. 

Silver. 

Copper.    I      Zinc. 

PARTS. 

9 

12 

3 

2 
I 

I 
I 
11.94 
10 

2 

7 
2 

o-5 

2 
2 

54-74 
5 

I 

3 
i 

0-5 

2 
28.17 

5.01 

I 

Soft        «       "        "        750  

"        «        «        ,-g,. 

"        "         "        less  than  583 

«        «         a          <t       «       « 

Solder  readily  fusible  «  

«           «     '      «       for  yellow  gold  

of  the  melting-points  of  some  metals. 


Metals. 

Degrees 
Fahrenheit. 

Metals. 

Degrees 
Fahrenheit. 

Tin  

86 

Gold    

2372 

Lead  .... 

CO 

Zinc    

773  6 

Nickel 

2912 

Antimony  

809  6 

Steel                            .    .    . 

3OQ2  to    3AC2 

Brass  

rgCQ 

IOOA 

3452  o  3  12 

of  high  temperatures. 


Description. 

Degrees 
Fahrenheit. 

Description. 

Degrees 
Fahrenheit. 

Incipient  red  heat  «...    .  . 

977 

A  red  heat  

77 
080 

1877 

A  dull  red  heat  visible  in 

10/j 
1006 

IOOO 

-jOOO 

Heat  of  a  common  fire  .... 

1140 

I2OO 

Heat    of    a    good    blast 

33OO 

Dull  red  heat 

I7IO 

oov-"-< 

specific  gravity  and  content  of  solutions  of  potassium 
carbonate  at  57.2°  Fahrenheit,  according  to  Gerlach. 


Potassium 
carbonate, 
per  cent. 

Specific  gravity. 

Potassium 
carbonate, 
per  cent. 

Specific  gravity. 

Potassium 
carbonate, 
per  cent. 

Specific  gravity. 

2 

1.01829 

20 

I.I9286 

38 

1.39476 

4 

1.03658 

22 

I.2I402 

40 

1.41870 

6 

i^>5513 

24 

1-23517 

42 

1.44338 

8 

1.07396 

26 

1.25681 

44 

1.46807 

10 

1.09278 

28 

1.27893 

46 

1.49314 

12 

1.11238 

30 

1.30105 

48 

I.5l86l 

H 

1.13199 

32 

1.32417 

5° 

1.54408 

16 

1.15200 

34 

1.34729 

52 

1.57048 

18 

1.17243 

36 

1.37082 

52.024 

1.57079 

470 


APPENDIX. 


Table  showing  the  specific  gravity  of  sulphuric  acid  at  59°  F., 
according  to  Kolb. 


Degrees  Baum6.  1 

Specific 
gravity. 

ico  parts  by 
weight 
contain 

One  litre 
contains  in 
kilogrammes 

«oJ 

1 

tx 

Q 

Specific 
gravity. 

ico  parts  by 
weight 
contain 

One  litre 
contains  in 
kilogrammes 

S03. 

H2S04. 

SO3. 

H2S04. 

S03. 

H2SO4. 

SO3. 

H2S04. 

o 

I.  COO 

0.7 

0.9 

0.007 

0.009 

34 

.308 

32-8 

40.2 

0.429 

0.526 

i 

1.007 

J-5 

1.9 

0.015 

0.019 

35 

.320 

33.8 

41.6 

0.447 

0-549 

2 

1.014 

2-3 

2.8 

0.023 

0.028 

36 

•332 

35-1 

43-o 

0.468 

0-573 

3 

1.022 

3-i 

3-8 

0.032 

0.039 

37 

•345 

36.2 

444 

0.487 

0-597 

4 

1.029 

3-9 

4.8 

0.040 

0.049 

38 

•357 

37-2 

45-5 

0.505 

0.617 

5 

1-037 

4-7 

5.8 

0.049 

c.o6o 

39 

•37° 

38.3 

46.9 

0-525 

0.642 

6 

1.045 

5.6 

6.8 

0.059 

0.071 

40 

•383 

39.5 

48.3 

0.546 

0.668 

7 

1.052 

6.4 

7.8 

0.067 

0.082 

4i 

•397 

40.7 

49-8 

0.569 

0.696 

8 

1.  060 

7.2 

8.8 

0.076 

0.093 

42 

1.410 

41.8 

51.2 

0.589 

0.722 

-9 

1.067 

8.0 

9-8 

0.085 

0.105 

43 

1.424 

42.9 

52.8 

0.611 

0.749 

10 

1-075 

8.8 

10.8 

0.095 

0.116 

44 

1.438 

44.1 

54-0 

0.634 

0.777 

ii 

1.083 

9-7 

11.9 

0.105 

0.129 

45 

MS  3 

45-2 

55-4 

0.657 

0.805 

12 

I.O9I 

10.6 

13.0 

0.116 

0.142 

46 

1.468 

46.4 

56-9 

0.681 

0.835 

13 

.100 

H-5 

14.1 

0.126 

0.155 

47 

1.483 

47.6 

58-3 

0.706 

0.864 

H 

.108 

12.4 

15.2 

0.137 

o.i  68 

48 

1.498 

48.7 

59.6 

0.730 

0.893 

15 

.116 

13.2 

16.2 

0.147 

0.181 

49 

i-SH 

49-8 

61.0 

o-754 

0.923 

16 

.125 

14.1 

'7-3 

0.159 

0.195 

5° 

1.530 

51.0 

62.5 

0.780 

0.956 

'7 

.134 

*5'* 

18.5 

0.172 

O.2IO 

5i 

1.540 

52.2 

64.0 

0.807 

0.990 

18 

.142 

1  6.0 

19.6 

0.183 

0.224 

52 

1-563 

53-5 

65.5 

0.836 

1.024 

19 

.152 

17.0 

20.8 

0.196 

0.233 

53 

1.580 

54-9 

67.0 

0.867 

1.059 

20 

.162 

1  8.0 

22.2 

0.209 

0.258 

54 

1-597 

56.0 

68.6 

0.894 

1.095 

21 

.171 

19.0 

23.3 

0.222 

0.273 

55 

1.615 

57.i 

70.0 

0.922 

1.131 

22 

.180 

2O.O 

24.5 

0.236 

0.289 

56 

1.634 

584 

71.6 

0-954 

1.170 

23 

.190 

21.  1 

2.S.8 

0.251 

0.307 

57 

1.652 

59-7 

73-2 

0.986 

1.  210 

24 

.200 

22.1 

27.1 

0.265 

0.325 

58 

1.672 

61.0 

74-7 

1.019 

1.248 

25 

.210 

23.2 

28.4 

0.281 

0.344 

59 

1.691 

62.4 

76.4 

1.055 

1.292 

26 

.220 

24.2 

29.6 

0.295 

0.361 

60 

1.711 

63.8 

78.1 

1.092 

1.336 

27 

.231 

25-3 

31.0 

0.3II 

0.382 

61 

1-732 

65.2 

79-o 

.129 

1.384 

28 

.241 

26.3 

32.2 

0.326 

0.400 

62 

!-753 

66.7 

81.7 

.169 

1.432 

29 

.252 

27.3 

334 

0.342 

0.418 

63 

1-774 

68.7 

84.1 

.219 

1.492 

30 

.263 

28.3 

34-7 

0-357 

0.438 

64 

1.796 

70.6 

86.5 

.268 

1-554 

31 

.274 

29.4 

36.0 

0.374 

0.459 

65 

1.819 

73-2 

89.7 

•332 

1.632 

32 

.285 

30.5 

37-4 

0.392 

0.481 

66 

1.842 

81.6 

IOO.O 

•503 

1.842 

33 

.297 

31.7 

38.8 

0.411 

0.503 

.APPENDIX. 


471 


Table  of  the  specific  gravity  and  content  of  nitric  acid, 
according  to  Kolb. 


ri 

£  3 

Specific 

TOO  parts  con- 
tain at  32°  F. 

100  parts  con- 
tain at  59°  F. 

fi 

Specific 

loo  parts  con- 
tain at  32°  F. 

loo  parts  con- 
tain at  59°  F. 

bCrn 

gravity. 

* 

oii  ^ 

gravity. 

i 

™- 

HN03. 

N2O5. 

HN03.   N20S. 

F 

HN03. 

N20S. 

HN03. 

N205. 

o 

I.OOO 

o.o 

O.O 

O.2 

O.I 

28 

.242 

36.2 

31.0 

38.6 

33-1 

i 

1.007 

I.I 

0.9 

1.5 

1.3 

29 

.252 

37-7 

32.3 

40.2 

34-5 

2 

I.OI4 

2.2 

1.9 

2.6 

2.2 

30 

.261 

39-1 

33-5 

4L5 

35-6 

3 

1.022 

34 

2.9 

4.0 

3-4 

31 

-275 

41.1 

35-2 

43-5 

37-3 

4 

I.O29 

4-5 

3-9 

4.4 

32 

.286 

42.6 

36.5 

45'° 

38.6 

5 

1.036 

5'5 

4-7 

£3 

5-4 

33 

.298 

44-4 

38.0 

47.1 

40.4 

6 

1.044 

6.7 

5-7 

7.6 

6.5 

34 

.309 

46.1 

39-5 

48.6 

41.7 

7 

1.052 

8.0 

6.9 

9.0 

7-7 

35 

.321 

48.0 

41.1 

50.7 

43-5 

8 

1.  060 

9.2 

7-9 

10.2 

8-7 

36 

•334 

50.0 

42.9 

52.9 

45-3 

9 

1.067 

10.2 

8.7 

1  1.4 

9.8 

37 

.346 

51.9 

44-5 

55-o 

47.1 

10 

1-075 

II.4 

9.8 

12.7 

10.9 

38 

•359 

54-0 

46.3 

57-3 

49.1 

ii 

1.083 

12.6 

10.8 

14.0 

12.0 

39 

.372 

56.2 

48.2 

59-6 

51.1 

12 

I.O9I 

13.8 

u.8 

15.3 

I3.I 

40 

•384 

58.4 

50.0 

61.7 

52.9 

13 

1.  100 

15.2 

13.0 

16.8 

14.4 

41 

.398 

60.8 

52.1 

64-5 

55-3 

14 

1.108 

16.4 

14.0 

1  8.0 

15.4 

42 

.412 

63.2 

54-2 

67.5 

57-9 

15 

1.116 

17.6 

I5-1 

19.4 

1  6.6 

43 

.426 

66.2 

56.7 

70.6 

60.5 

16 

1.125 

18.9 

1  6.2 

20.8 

17.8 

44 

.440 

69.0 

74-4 

63-8 

ll 

I.I34 

20.2 

17-3 

22.2 

19.0 

45 

•454 

72.2 

61.9 

78.4 

67.2 

IS 

I-I43 

21.6 

18.5 

23-6 

20.2 

46 

.470 

76.1 

65.2 

83-0 

71.1 

19 

1.152 

22.9 

19.6 

24.9 

21.3 

47 

485 

80.2 

68.7 

87.1 

74-7 

20 

1.161 

24.2 

20.7 

26.3 

22.5 

48 

.501 

84-5 

72.4 

92.6 

79-4 

21 

1.171 

25.7 

22.0 

27.8 

23.8 

49 

.516 

88.4 

75.8 

96.0 

82.3 

22 

1.180 

27.0 

23.1 

29.2 

25.0 

49.5 

.5.24 

90.5 

77.6 

98.0 

84.6 

23 

.1.190 

28.5 

24.4 

30.7 

26.3 

49.9 

.530 

92.2 

79.0 

1  00.0 

85.71 

24 

1.199 

29.8 

25-5 

32.1 

27.5 

50.0 

.532 

92.7 

79-5 

— 

— 

25 

i.  210 

3M 

26.9 

33-8 

28.9 

50.5 

.541 

95-o 

81.4 

— 

— 

26 

1.  221 

33-i 

28.4 

35-5 

30.4 

S1-0}     -549 

97-3 

83.4 

— 

— 

27 

I.23I 

34-6 

29.7 

37-Q 

31.7 

5J-5     -559 

1  00.0 

85.71 



— 

Table  showing  the  specific  gravity  of  sal  ammoniac  solutions  at 
66.2°  F.,  according  to  Schiff. 


Content  of 

Content  of 

Content  of 

the  solution, 

Specific  gravity. 

the  solution, 

Specific  gravity. 

the  solution, 

Specific  gravity. 

per  cent. 

per  cent. 

per  cent. 

, 

I.OO29 

II 

1.0322 

21 

1.  0606 

2 

1.0058 

12 

I-035I 

22 

1.0633 

3 

1.0087 

13 

1.0380 

23 

1.  0660 

4 

1.0116 

H 

1.0409 

24 

1.0687 

5 

1.0145 

15 

1.0438 

25 

1.0714 

6 

1.0174 

16 

1.0467 

26 

1.0741 

7 

1.0203 

17 

1.0495 

27 

1.0768 

8 

1.0233 

18 

1.0523 

28 

1.0794 

9 

1.0263 

19 

1.0551 

29 

1.0820 

10 

1.0293 

20 

1.0579 

30 

1.0846 

4/2 


APPENDIX. 


Table  showing  the  electrical  resistance  of  pure  copper  wire 
of  various  diameters. 


No.  of  wire, 
Birmingham 
wire  gauge. 

Resistance  of 
i  foot  in  ohms. 

Number  of 
feet  required 
to  give 
resistance 
of  i  ohm. 

No.  of  wire, 
Birmingham 
wire  gauge. 

Resistance  of 
i  foot  in  ohms. 

Number  of 
feet  required 
to  give 
resistance 
of  i  ohm. 

0000 

0.0000516 

19358 

17 

0.00316 

3I6.I 

000 

0.0000589 

16964 

18 

0.00443 

225.5 

OO 
O 

0.0000737 
O.OOOO922 

13562 
10857 

19 

20 

0.00603 
0.00869 

165.7 
II5.I 

I 

O.OOOII8 

8452.6 

21                     O.OIO4O 

96.2 

2 

0.000132 

7575-1 

22 

0.01358 

73-6 

3 

0.000159 

6300.1 

23 

0.01703 

58.7 

4 

0.000188 

5319.9 

24 

O.O22CO 

45-5 

5 

0.000220 

4545-9 

25 

O.O266I 

37-6 

6 

0.000258             3870.3 

26 

0.03286 

30.4 

7 

0.000329           3043.4 

27 

0.04159 

24.0 

8 

0.000391            2557.1 

28 

0.05432 

18.4 

9 

0.000486               2057.7 

29 

0.06300 

15-9 

10 

0.000593             1686.5 

30            |         0.07393 

J3-5 

ii 

0.000739          1352.5 

31 

0.10646 

9-4 

12 

0.000896              1  1  1  6.0 

32 

0.13144 

7.6 

13 

0.001180                 847.7 

33 

0.16634 

6.0 

H 

0.001546 

647.0 

34 

0.21727 

4-6 

15 

0.002053 

487.0 

35 

0.42583 

2.4 

16 

0.002520 

396.8 

36 

0.66537 

1-5 

Resistance  and  conductivity  of  pure  copper  at  different 
temperatures. 


Centigrade 
temperature. 

Resistance. 

Conductivity. 

Centigrade 
temperature. 

Resistance. 

Conductivity. 

0° 

1.  00000 

1.  00000 

16° 

1.06168 

.94190 

I 

1.00381 

.99624 

17 

1.06563 

.93841 

2 

1.00756 

.99250 

18 

1.06959 

•93494 

3 

I.OH35 

.98878 

19 

1-07356 

.93148 

4 

I.OI5I5 

.98508 

20 

1.07742 

.92814 

5 

1.01896 

.98139 

21 

1.08164 

.92452 

6 

1.02280 

.97771 

22 

1-08553 

.92121 

7 

1.02663 

.97406 

23 

1.08954 

.91782 

8 

1.03048 

.97042 

24 

1.09365 

.91445 

9 

L03435 

.96679 

25 

1.09763 

.91110 

10 

1.03822 

.96319 

26 

1.  10161 

.90776 

ii 

1.04199 

•9597° 

27 

1.10567 

.90443 

12 

1.04599 

•95603 

28 

1.11972 

.90113 

J3 

1.04990 

.95247 

29 

1.11382 

.89784 

H 

1.05406 

.94893 

30 

1.11782 

*  .89457 

15 

L05774 

•94541 

APPENDIX. 


473 


Table  showing  actual  diameters  in  decimal  parts  of  an  inch 
corresponding  to  the  numbers  of  various  wire  gauges. 


No.  of  wire 
gauge. 

Roebling. 

Brown  & 
Sharpe. 

Birmingham 
or  Stubs. 

English  legal 
standard. 

Old  English 
or  London. 

000000 

.46 





.464 



oocoo 

•43 

— 

— 

•432 

— 

oooo 

•393 

.46 

•454 

•4 

•454 

ooo 

.362 

.40964 

•425 

.372 

•425 

00 

•331 

.3648 

.380 

•348 

•38 

0 

.307 

.32495 

.340 

.324 

••34 

i 

.283 

.2893 

•3 

•3 

•3 

2 

.263 

.25763 

.284 

.276 

.284 

3 

.244 

.22942 

•259 

.252 

.259 

4 

.225 

.20431 

.238 

.232 

.238 

5 

.207 

.18194 

.22 

.212 

.22 

6 

.192 

.16202 

.203 

.192 

.203 

7 

.177 

.14428 

.18 

.176 

.18 

9 

.162 
.148 

.  i  2849 
•  II443 

.165 
.148 

.16 
.144 

38 

10 

•135 

.10189 

•134 

.128 

.134 

ii 

.120 

.09074 

.12 

.116 

.12 

12 

.105 

.08081 

.109 

.104 

.109 

*3 

.092 

.07196 

.095 

.092 

•095 

H 

.08 

.06408 

.083 

.08 

.083 

15 

.072 

.05706 

.072 

.072 

.072 

16 

.063 

.05082 

•065 

.064 

.065 

*7 

.054 

•04525 

.058 

.056 

.058 

18 

.047 

.0403 

.049 

.048 

.049 

19 

.041 

.03589 

.042 

.04 

.04 

20 

•035 

.03196 

.035 

.036 

•035 

21 

.032 

.02846 

.032 

.032 

.0315 

22 

.028 

•02534 

.028 

.028 

.0295 

23 

.025 

.02257 

.025 

.024 

.027 

24 

.023 

.0201 

.022 

.022 

.025 

25 

.02 

.0179 

.02 

.02 

.023 

26 

.018 

.01594 

.018 

.018 

.O2O5 

27 

.017 

.01419 

.016 

.0164 

.01875 

28 

.Ol6 

.01264 

.OI4 

.0148 

.0165 

29 

.015 

.01125 

.013 

.0136 

•OI55 

30 

.014 

.01002 

.OI2 

.0124 

•01375 

31 

•0135 

.00893 

.010 

.0116 

.01225 

32 

.013 

.00795 

.009 

.0108 

.01125 

33 

.Oil 

.00708 

.008 

.01 

.01025 

34 

.OI 

.0063 

.007 

.OO92 

.0095 

35 

.0095 

.00561 

.005 

.0084 

.009 

36 

.009 

.005 

.004 

.0076 

•0075 

474 


APPENDIX. 


Weight  of  iron,  copper,  and  brass  wire  and  plates. 

(Diameters  and  thickness  determined  by  American  gauge.) 


.No.  of 
gauge. 

Size  of 
each 
No. 

WEIGHT  OF  WIRE  PER  1000 
LINEAL  FEET. 

WEIGHT  OF  PLATES  PER 
SQUARE  FOOT. 

Wro't 
iron. 

Steel. 

Copper. 

Brass. 

Wro't 
iron. 

Steel. 

Copper. 

Brass. 

at. 

Inch. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

0000 

.46000 

560.74 

566.03 

640.51 

605.18 

I7-25 

17.48 

20.838 

19.688 

oooT 

.40964 

444.68        448-88 

5°7-95 

479.91 

15.3615 

15-5663 

18557 

17-533 

oo 

.36480 

352-66 

355-99 

402.83 

380.67 

13-68 

13.8624 

16.525 

15-613 

o 

.32486 

279.67 

282.30 

3*9-45 

301.82 

12.1823 

I2-3447 

14.716 

13.904 

I 

.28930 

221.79 

223.89 

253-34 

239-35 

10.8488 

.  10.9934 

13-105 

12.382 

2 

•25763 

175-89 

I77-55 

200.91 

189.82 

9.6611 

9.7899 

11.671 

11.027 

3 

.22942 

13948 

140.80 

I59-32 

150.52 

8.60^3 

8.7180 

10.393 

9.8192 

4 

.20431 

110.62 

in.  66 

126.35 

119.38 

7.6616 

7-7638 

9-2552 

8-7445 

5 

.18194 

87.720 

88.548 

IOO.2O 

94.666 

6.8228 

6.9*37 

8.2419 

7-787 

6 

I 

.16202 
.14428 
.12849 

69-565 
55-165 
43-751 

70.221 

55-685 
44.164 

79.462 
63.013 
49.976 

75.075 
59-545 
47.219 

6.0758 
5-4105 
4.8184 

6.1568 
5.4826 
4.8826 

7-3395 
6.5359 
5.8206 

6-9345 
6.1752 

9 

•II443 

34-699 

35.026     i   39.636 

37-437 

4.2911 

4-3483 

5-1837 

4.8976 

10 

.10189 

27.512 

27-772     j   3J-426 

29.687 

3.8209 

3-8718 

4.6156 

4-3609 

ii 

.090742 

21.820 

22.026         24.924 

23-549 

3.4028 

3.4482 

4.1106 

3-8838 

12 

.080808 

17-304 

17.468 

19.766 

18.676 

3-0303 

3.0707 

3.6606 

3.4586 

13 

.071961 

13.722 

13-851 

I5-674 

14.809 

2.6985 

2-7345 

3-2598 

3.0799 

*4 

.064084 

10.886 

10.989 

12.435 

11.746 

2.4032 

2.4352 

2.9030 

2.7428 

15 

.057068 

8.631 

8.712 

9-859 

9-3I5 

2.1401 

2.1686 

2.5852 

2.4425 

16 

.650820 

6.845 

6.909 

7.819 

7-587 

1-9058 

1.9312 

2.3021 

2.1751 

J7 

•045257 

5.427 

5.478 

6.199 

1.6971 

1.7198 

2.0501 

1-937 

18 

.040^03 

4-304 

4-344 

4.916 

4  645 

I.5II4 

i-53I5 

.8257 

1-725 

19 

.035890 

3-4*3 

3-445 

3.899 

3.684 

1-3459 

1.3638 

.6258 

20 

.031961 

2.708 

2-734 

3.094 

2.920 

1.1985 

1.2145 

1.4478 

1.3679 

21 

.028462 

2.147 

2.167 

2.452 

2.317 

1.0673 

1.0816 

.2893 

1.2182 

22 

•025347 

1.719 

1-945 

1.838 

•95051 

.96319 

.14*3 

1.0849 

23 

.022571 

1.350 

1-363 

1.542 

1-457 

.84641 

•8577 

1.0225 

.96604 

24 

.020100 

1.071 

1.081 

1.223 

•75375 

.7638 

•91053 

.86028 

25 

.017900 

0.8491 

0.8571 

.9699 

0.9163 

.67125 

.6802 

.81087 

.76612 

26 

.015941 

0.6734 

0.6797 

.7692 

0.7267 

•59775 

.60572 

.72208 

.68223 

27  • 

.014195 

0.5340 

0-5391 

.6099 

0.5763 

.53231 

•53941 

•64303 

•60755 

28 

.012641 

0.4235 

0-4275 

.4837 

0.4570 

•474°4 

.48036 

•57264 

•54103 

29 

.011257 

0.3358 

0-3389 

•3835 

0.3624 

.42214 

.42777 

.50994 

.48180 

30 

.010025 

0.2663 

0.2688 

•3042 

0.2874 

•37594 

•38095 

•45413 

,42907 

31 

.008928 

0.2113 

0.2132 

•2413 

0.2280 

.3348 

.33926 

.40444 

.38212 

32 

-007950 

0.1675 

0.1691 

o.i  808 

•29813 

.3021 

.36014 

.34026 

33 

.007080 

0.1328 

0.1341 

.1517 

0.1434 

•  2655 

.26904 

.32072 

.30302 

34 

.006304 

0.1053 

0.1063 

.1204 

0.1137 

.2364 

•23955 

.28557 

.26981 

35 

.005614 

0.08366 

0.08445 

.0956 

0.1015 

.21053 

•21333 

•2543i 

.24028 

36 

.OO5OOO 

.06625 

.06687 

•°757 

.0715 

•1875 

.19 

.2265 

.2140 

37 

•004453 

•05255 

-05304 

.06003 

.05671 

.16699 

.16921 

.20172 

.19059 

38 

.003965 

.04166 

.04205 

.04758 

.04496 

.14869 

.15067 

.17961 

•i6973 

39 

.003531 

.03305 

.03336 

•03755 

.03566 

.13241 

.13418 

•15995 

.1511 

40 

•003144 

.02620 

.02644 

.02992 

.02827 

.1179 

.11947 

.14242 

•13456 

Specific  grav. 
Weight  per 
cubic  foot. 

7-7747 

185.874 

7.847 
00-45 

8.880 

8.386 
524-16 

7.200 
450. 

7.296 
456- 

8.698 
543-6 

8.218 
5I3.6 

APPENDIX.  475 

Rules  for  Speed. 

To  find  speed  of  counter-shaft  in  accordance  with  main  shaft 
and  machine. — Subtract  the  number  of  revolutions  of  the  main 
shaft  from  the  number  of  revolutions  the  machine  should  make; 
divide  the  remainder  by  two.  The  quotient  will  show  the 
number  of  revolutions  of  the  counter-shaft. 

Example. — The  main  shaft  runs  200  revolutions  per  minute, 
while  the  machine  should  run  1000  revolutions  per  minute. 
Deduct  200  from  1000,  leaving  800,  which  divide  by  2;  the 
quotient  will  then  be  400,  which  is  the  number  of  revolutions 
the  counter-shaft  should  make. 

To  find  diameter  of  pulley  on  the  main  shaft. — Multiply  the 
diameter  in  inches  of  the  receiving  pulley  of  the  counter-shaft 
by  the  number  of  revolutions  the  counter-shaft  should  make 
and  divide  the  product  by  the  number  of  revolutions  the  main 
shaft  makes. 

Example. — The  counter-shaft  makes  400  revolutions,  the 
receiving  pulley  is  7*^  inches  in  diameter  and  the  main  shaft 
makes  200  revolutions;  400  times  7J^  equals  3000,  which 
divided  by  200  equals  1 5  ;  this  is  the  diameter  in  inches  of  the 
pulley  on  the  main  shaft. 

To  find  diameter  of  pulley  on  counter- shaft  carrying  belt  to 
machine. — Multiply  the  number  of  revolutions  the  machine 
should  make  by  the  diameter  of  pulley  of  the  machine  and 
divide  by  the  number  of  revolutions  the  counter-shaft  makes. 

Example. — Say  the  machine  should  make  1000  revolutions, 
the  diameter  of  pulley  on  machine  being  6  inches,  and  the 
counter-shaft  making  400  revolutions ;  then  multiplying  1000 
by  6  equals  6000:  dividing  this  by  400  gives  15,  which  should 
be  the  diameter  of  the  pulley  carrying  belt  from  counter-shaft 
to  machine. 

To  find  the  speed*  of  a  machine. — Multiply  the  number  of 
revolutions  of  the  main  shaft  by  the  diameter  of  pulley  in 
inches,  and  divide  by  the  diameter  of  receiving  pulley  of  the 
counter-shaft.  The  result  is  the  speed  of  the  counter-shaft. 
Then  multiply  the  number  of  revolutions  of  counter-shaft  by 


4/6  APPENDIX. 

diameter  of  transmitting  pulley,  and  divide  by  diameter  of 
pulley  on  machine.  The  result  will  be  the  speed  of  the 
machine.  It  should  be  well  understood  that  no  other  pulleys 
but  those  in  contact  with  one  belt  should  be  considered. 

Comparison  of  the  Scales  of  the  Fahrenheit,  Centigrade,  and 
Reaumur  Thermometers,  and  Rules  for  Converting  one  Scale 
into  another. 

These  three  thermometers  are  graduated  so  that  the  range  of 
temperature  between  the  freezing  and  boiling  points  of  water  is 
divided  by  Fahrenheit's  scale  into  180  (from  32°  to  212°), 
by  the  Centigrade  into  100  (from  o°  to  100°),  and  by  that  of 
Reaumur  into  80  (from  o°  to  80°)  portions  or  degress. 

The  spaces  occupied  by  a  degree  of  each  scale  are  consequently 
as  |,  \,  and  \  respectively,  or  as  I,  1.8,  and  2.25  ;  and  the  num- 
ber of  degrees  denoting  the  same  temperature,  by  the  three 
scales,  when  reduced  to  a  common  point  of  departure  by  sub- 
tracting 32  from  Fahrenheit's,  are  as  9,  5,  and  4.  Hence,  we 
derive  the  following  equivalents:  — 

A  degree  of  Fahrenheit's  is  equal  to  0.5  of  the  Centigrade  or 
to  0.4  of  Reaumur's;  a  degree  of  centigrade  is  equal  to  1.8  of 
Fahrenheit's  or  to  0.8  of  Reaumur's  ;  and  a  degree  of  Reaumur's 
is  equal  to  2.25  of  Fahrenheit's,  or  to  1.25  of  the  Centigrade. 

To  convert  degrees  of  Fahrenheit  into  the  Centigrade  or 
Reaumur's,  subtract  32  and  multiply  the  remainder  by  f  for  the 
centigrade  or  |-  for  Reaumur's. 

To  convert  degrees  of  the  Centigrade  or  Reaumur's  into 
Fahrenheit's,  multiply  the  centigrade  by  -f,  or  Reaumur's  by  f , 
as  the  case  may  be,  and  add  32  to  the  product. 


INDEX. 


A  CCUMULATORS,  377,  378  | 

J\     Acid  copper  baths,  vats  for,  104, 

105 

free,  in  galvanoplastic  baths, 

determination  of,  365,  366 

mixtures,    recovery   of  gold 

from,  318 
neutralization   of   the  effect 

of,  421 

potassium  carbonate,  438 
recovery  of,  from  exhausted 

dipping  baths,  155, 156 
vapors,  absorbing  plant  for, 

154,  155 
Acids,  424-428 

organic,  salts  of  the,  446-448 
Action,  local,  29 

Air,  renewal  of,  in  plating  rooms,  85 
Alkalies  and  alkaline  earths,  428,  429 

poisoning  by,  423 
Alkaline  earths  and  alkalies,  428,  429 

platinate  bath,  320,  321 
Alliance  machine,  the,  78 
Alloy   containing   nickel,  deposition 

of  an,  219 
Alloys, metallic,  for  preparing  moulds, 

389,  390 

first  deposition  of,  6 
most  usual,    and    solders,    table 
showing    the    composition   of, 
466-469 

nickel,  deposits  of,  219-221 
table  of,  467 
Alternating  current  machines,  66 

currents,  25 

Aluminium  baths,  348-350 
deposition  of,  348-352 
electro-deposition  upon,  350-352 
new  method  for  the  electro-depo- 
sition of,  349 

potassium  sulphate,  440,  441 
properties  of,  348 

American  double  polishing  lathes,  139 
Ammeter,  113 

Westoti,  102 
Ammonia,  429 
Ammonium  alum,  441 


Ammonium  chloride,  431 
hydrate,  429 
phosphate,  446 
sulphate,  440 
sulphide,  430 
Ampere,  the,  31 

theory  or  hypothesis  of,  11,  12 
Amperemeter,  113 
Anious,  26 
Anode,  26 

surface,  size  of,  183  . 
wire,  103 

coupling  the,  with  the  resist- 
ance     boards,     voltmeter, 
shunt  and  baths,  114 
wires,  insulation  of,  111 
Anodes,  choice  of,  166 

for  brass  bath,  244,  245 
copper  baths,  231 
galvanoplastic  baths,  365 
nickeling  sheet  zinc,  208 
insoluble,  166,  181 

platinum  in  silvering,  253 
nickel,  180-184 

reddish  tinge  of,  184 
platinum,  293 

proportion  of  cast,  to  rolled,  177 
silver,  251-260 

use  of  steel  plates  in  place  of, 

253 

suspension  of,  107 

Antimony  and  arsenic,  deposits  of, 
by  contact  and  immersion,  347, 
348 

baths,  345,  346 
deposition  of,  345,  346 
-potassium  tartrate,  447 
properties  of,  345 
sulphide,  430 
-  trichloride,  431,432 
Antique  silvering,  282,  283 
Apparatus  and  instruments,  various, 

448-453 

Aqua  fortis,  425 
Areas  silvering,  259,  260 
Armature,  64 
Gramme,  67 


(477) 


478 


INDEX. 


Arsenic  and  antimony,  deposits  of,  by 
contact  and  immersion,  347, 348 
baths,  346,  347 
deposition  of,  346-348 
poisoning  by,  423 
properties  of,  346 
trisulphide,  431 
white,  427 
Arseuious  acid,  427 

addition  of,  to  brass  baths, 

240 

chloride,  432 
sulphide,  431 
Art-castings,    coppered,    inlaying    of 

depressions  of,  237,  238 
Astatic  galvanometer,  22 
Auric  chloride,  434 
Australia,  gold  composition  of,  287 
Auxiliary  apparatus,  93 

SACKING,  382 
Baking  powder,  439 
lance,  plating,  263-266 
Bath,  bright  dipping,  152,  275 

conditions  required  to  guarantee 

good  performance,  167 
electrolytic,  requisites  of  a,  162 
working  the,    with  the    electric 

current,  165 

Baths,  acid  copper,  vats  for,  104,  105 
agitation  of,  162-164 
aluminium,  348-350 
antimony,  345,  346 
arsenic,  346,  347 
brass,  238-243 
bronze,  247,248 
cobalt,  222 
concentration  of,  161 
conclusion  as  to  the  condition  of, 

from    changes  in   the  specific 

gravity,  161,162 
containing    potassium     cyanide, 

holders  for,  105 
filtering  of,  166 

for  gilding  by  contact,  305,  306 
dipping,  308-310 
gold,  288-293 
heating  of,  86,  87 
lead,  338 

nickel,  vats  for,  104,  105 
palladium,  325 
platinum,  319-322 
steel,  341-344 
temperature  of,  162 
tin,  327-329 

to  secure  lasting  qualities  to,  166 
vats  for  heating,  105 
Batteries,  bichromate,  53-57 


Batteries,  plunge,  53-57 

storage,  electro-chemical  process 

of  forming,  378 

Battery,    copper-bath     for     galvano- 
plastic  depositions  with  the,  362 
Foote's  pinnacle  gravity,  43,  44 
galvanoplastic    depositions  with 

the,  360,  361 
reduction   of  metals  without  a, 

168,  169 
Stoehrer's,  56 
stripping    nickeled    articles    by 

the,  196 
trough,  2,  32 
Baume's  hydrometer,  450 
Beardslee,    G.    W.,    cobalt    solution 

recommended  by,  223 
Becquerel's  element,  35 
Bell  metal,  238 
Bells,  coloring  of,  341 
Belt  strapping  attachment  or  endless 

belt  machine,  142,  143 
Benzine,  removal  of  grease  with,  156, 

157 
Bertrand,  aluminium  bath  according 

to,  348 

palladium  bath  according  to,  325 
Bicarbonate  of  potash,  438 
Bichromate  batteries,  53-57 
Bicycles,  nickeling  parts  of,  186 
Binding  posts,  107 

screws,  107 
Bird,  production  of  the  amalgams  of 

potassium  and  sodium  by,  4 
Black  color  on  copper,  405 
lead,  gilt,  373 

mixture    of,    with     bronze 

powder,  373,  374 
silvered,  373 
-leading,  372 

machine,  372 
wet  process  of,  372 
lustrous  on  iron,  414,  415 
nickeling,  344 
on  zinc,  413 

sulphide  of  antimony,  430 
Blue  on  iron,  416 
steel,  416 
black  on  copper,  405 

zinc,  413 

gray  shades  on  copper,  405 
vitriol,  441,  442 

pure,    table   of  approximate 
content  of,  at  different  de- 
grees Be.,  and  at  59°  F.,  358 
Bobs,  cloth,  137 

construction  of,  200,  201 
polishing,  137 


INDEX. 


479 


Boettger  on  the  deposition  of  nickel 

from  its  double  salts,  6 
platinum  bath  of,  319 
steel  bath  according  to,  341,  342 
tinning  solution  according  to,  332 
Boiling,  nickeling  by,  217-219 
pans,  164,  165 
tinning  by,  330,  331 
Boracic  acid,  426,  427 
Boric  acid,  426,  427 

as  addition  to  nickeling  baths, 

171,  172 
Bossard      Mechano  -  Electroplating 

tanks,  455-461 
Bouant's   method    of   amalgamating 

zinc,  34 
Brandley,  directions  by,  for  preparing 

gelatine  moulds,  397 
plating  balance  used  by,  263-266 
Brass  and  bronzes,  coloring  of,  408-412 
articles,  cobalting,  223,  224 

small,  tinning  solution  for, 

331,332 
superficial  coating  of  tin  on, 

333 

bath,  constitution  of  a,  238,  239 
formation   of   slime   on    the 

anodes  in  the,  245 
regulation  of  a,  245,  246 
'    with  cuproso-cupric  sulphite, 

241 
baths,  238-243 

anodes  for,  244,  245 
density  of  current  for,  243 
irregular  working  of,  240 
bronze  and  copper,  deposition  of, 

225-248 
brown  color  called  bronze  Barbe- 

dienne  on,  410 
casting  of,  with  zinc,  337 
castings,  grinding  of,  136 
coloring  of,  347 

color  resembling  gold  on,  409,  410 
corn-flower  blue  on,  411 
deposits,  polishing  of,  149 
Ebermayer's  experiments  in  col- 
oring, 411,  412 

gray  color  with  a  bluish  tint  on,  409 
lustrous  black  on,  408 
nickel  bath  for,  178 
nielling  upon.  282 
objects,  dead  or  dull  surface  on, 

153 

tinning  of,  327 
pale  gold  color  on,  409 
pickling  of,  151,152 
production  of  a  grained  surface 
on,  by  pickling,  156 


Brass,  properties  of,  238 
red,  238 

removal  of  oxide  from,  158 
scratch  brushes  for,  146 
sheet,  nickeling,  209 
sheets,  polishing  of,  136 
steel  gray  on,  408,  409 
straw   color,   to   brown,  through 
golden     yellow,    and    tornbac 
color  on,  409 

various  colors  upon,  407,  408 
violet  on,  411 

wire  and  plates,  weights  of,  474 
yellow,  238 

Brassed  articles,  inlaying  of,  247 
Brassing,  238-247 

by  contact  and  dipping,  247 

color  of,  244 

distance  of  objects  in,  from' the 

anodes,  246 
execution  of,  243-247 
sheet  zinc,  206 

unground  iron  castings,  246,  247 
Bright  dipping  bath,  152 

Platinum  Plating  Co.,  of  London, 
platinum  bath,  patented  by,  320 
Britannia,  preparation  of,  for  silver- 
ing, 268-270 

removal  of  oxide  from,  158 
Bronze  articles,  clay  yellow  to  dark 

brown  on,  410 
dead  yellow  on,  410 
Barb£dienne  on  brass,  410 
baths,  247,  248 
brass  and  copper,  deposition  of, 

225-248 

-like  patina  on  tin,  416 
nickeling  of,  151 ,  152 
removal  of  oxide  from,  158 
Bronzes,  238 

and  brass,  coloring  of,  408-412 
Bronzing,  247,  248 
execution  of,  248 
on  zinc,  413,  414 
Brown  black  with  bronze  lustre  on 

iron,  416 
color  called  bronze  Barbddienne 

on  brass,  410 
on  copper,  404,  405 
Bruce,  addition  of  bisulphide  of  car- 
bon to  nickel  baths,  recommended 
by,  179 
Brugnatelli,  first  practical  results  in 

electro-gilding  attained  by,  3 
Brush  coppering,  236,  237 

dynamo,  70-72 
Brushes,  126 

collecting,  64 


480 


INDEX. 


Bunsen  element,  37-40 

elements   for   galvanoplastic  de- 
positions, 360,  361 
location  of,  86 
manipulation  of,  42,  43 
plunge  battery,  53 
Burning,  187 
Burnishers,  149 
Burnishing,  144,  145 
machines,  267 
operation  of,  149,  267 
Busts,  galvanoplastic  reproduction  of, 

388, 389 

Butter  of  antimony,  431 ,  432 
zinc,  432,  433 

/CALCIUM  carbonate,  439 

I,         hydrate,  429 

California  gold,  composition  of,  287 

Capsules  or  evaporating  dishes,  448 

Carbonates,  438-440 

Carbon,   bisulphide   of,    addition   of, 

to  nickel  baths,  179 
disulphide  or  bisulphide,  430 
Carboy  rocker,  158,  159 
Carlisle   and  Nicholson,    decomposi- 
tion of  water  by,  3 
Cast-iron,  bath  for  brassing,  242 
coating  with  bronze,  247 
objects,  pickling  of,  150,  151 
tinning  of,  328 
zinc  bath  for,  335 
Casts,  plaster  of  Paris  for,  390-393 
Cathode,  26 
Cations,  26 
Caustic  potash,  428 

soda,  428 
Cell  apparatus,  354-358 

copper  bath  for  the, 

358 

galvanoplastic    depo- 
sition in  the,  354- 
359 
Cellulose  lacquers  and  varnishes,  417- 

419 

Centigrade,  Reaumur  and  Fahrenheit 
thermometers,   comparison    of  the 
scales  of  the,  and  rules  for  convert- 
ing one  scale  into  another,  476 
Chain,  galvanic,  16 
Chalk,  439 
Check  voltmeter,  454 
Chemical  and  electro-chemical  equiv- 
alents, table  of,  462,  463 
products  and   various  apparatus 
and  instruments  used  in  electro- 
plating, 424-453 
Chemicals,  purity  of,  160 


Chile  saltpetre,  444 

Chloride  of  silver,  reduction  of,  286 

Chlorine  combinations,  431-435 

poisoning  by,  423,  424 
Christofle   &   Co.,    experiments    by, 
with  magneto-electrical  machines, 
7,8 

Chromes,  metallic,  339-341 
Chromic  acid,  427,  428 
Chromium  combination,  soluble,  41 
Circuit,  closing,  16 
Citric  acid,  426 

Clamond's  thermo-electric  pile,  58,  59 
Clarke,  electric   generator   produced 

by,  65 

Clausius's  theory  of  molecules,  26,  27 
Clay,  metallization  of,  400 

cells,  filling  of,  375,  376 
Cleansing  apparatus,  108 
Cliches,  cell  apparatus  for  producing, 
355,  356 

nickeling,  214-216 
Closing  circuit,  16 
Cloth  bobs,  137 
Cobalt-ammonium  sulphate,  443 

and  nickel,  deposition  of,  169-225 

baths,  222 

carbonate,  440 

chloride,  433 

properties  of,  221 

sulphate,  443 
Cobalting,  221-225 

articles  en  masse,  223 

by  contact,  224,  225 

small    fancy   articles,    bath    for, 

223,  224 

Coins,  taking  casts  from,  390,  391 
Colcothar,  144 

Cold  gilding,  bath  for,  289,  290 
Collecting  brushes,  the,  64 
Collector,  the,  64 

Coloring  brass  and  bronzes.  408-412 
Bbermayer's     experi- 
ments in,  411,  412 

iron,  414-416 

patmizing,   oxidizing  of  metals, 
403-417 

silver,  417 

tin,  416 

zinc,  413,  414 
Common  salt,  431 
Commutator,  the,  64 

cylinder,  64 

Compress  polishing  wheels,  137,  138 
Conducting    rods,    arrangement    of, 

106,  107 

fixing    of,    on    vats, 
105,  106 


INDEX. 


481 


Conducting  salts,  171 
wires,  103 

calculating  the  thickness  of, 

120,  121 
Conductor,  development  of  heat   in 

the,  29 

resistance  of  a,  17 
Conductors,  bad,  13 

good,  13 

Contact,  brassing  by,  247 
cobalting  by,  224,  225 
coppering  by,  235,  236 
deposits  of  antimony  and  arsenic 

by,  347,  348 

electricity,  discovery  of,  1 
electro-deposition  by,  108,  169 
gilding  by,  305-308 
immersion  and   friction,  gilding 

by,  305-312 
leading  by,  339 
nickeling  by,  217-219 
platinizing  by,  324 
silvering  by,  271-277 
steeling  by,  345 
tinning  by,  330,  331 
zincking  iron  by,  337 
Continuous  current  machines,  (56 
Copper  acetate,  447 

-alloys,  current  for  nickeling,  188 
dead  or  dull  surface  on,  153 
silvering  articles  of,  275,  276 
articles,  cobalting,  223.  224 

small,  tinning  solution   for, 

331,332 

stripping  of,  316 
superficial  coating  of  tin  on, 

333 
bath,  Delval's,  351 

for  the  cell  apparatus,  358 
removal  of  acid  from,  359 
with  cupron,  229 

sulphate  of  copper,  228, 

229 
baths,  225-231 

anodes  for,  231 
for     galvanoplastic     deposi- 
tions with  a  separate  source 
of  current,  361-365 
phenomena     appearing     in, 

231,232 
vats  for,  231 
with  cuproso-cupric  sulphite, 

229 
without   potassium  cyanide, 

229,  230 

black  color  on,  405 
blue-black  color  on,  405 
blue-gray  shades  on,  405 

31 


Copper,  brass  and  bronze,  deposition 

of,  225-248 
bronzing  of,  405 
brown  color  on,  404,  405 
carbonate,  439 
castings,  grinding  of,  136 
chemically  pure,  352 
chloride,  432 
coating     black  leaded     surfaces 

with,  373 
grasses,    leaves  and    flowers 

with,  399 

laces  and  tissues  with,  398 
mercury  vessels  of  thermom- 
eters with,  400 
of,  with  zinc,  337 
wood   with  a  galvanoplastic 

deposit  of,  399.  400 
wooden   handles  of  surgical 

instruments  with,  400 
coloring  of,  347,  403-408 
current  for  nickeling,  188 
cyanides,  436,  437 
dark  steel-gray  color  on,  407 
dead  black  on,  4()o,  406 
deep  black  color  on,  406 
deposited  by  electrolysis,  physi- 
cal properties  of,  352 
deposits,  polishing  of,  149 
determination  of  content  of,  in 

galvanoplastic  baths,  366,  367 
determination  of  content  of,  re- 
quired for  a  beautiful  red  gold, 
299 

determination  of  quantity  of,  dis- 
solved   in    stripping    cobalted 
copper  plates,  222,  223 
for  galvanoplastic  purposes,  352, 

353 

galvanoplastic  depositions,  elas- 
ticity, strength  and  hardness 
of,  362 

Hiibl's  experiments  with,  353 
massive,  various  colors  upon,  407. 

408 

nickel  bath  for,  178 
objects,  tinning  of,  327 
pale  red  of  copper  color  to  dark 

chestnut-brown  on,  403,  404 
pickling  of,  151,  152 
plates,  facing  of,  with  cobalt,  222 
polishing  of,  136 
printing     plates,     galvanoplastic 

bath  for,  362 
steeling  of,  342,  343 
properties  of,  225 
pure,  resistance  and  conductivity 
of,  472 


482 


INDEX. 


Copper,  red  brown  color  on,  405 

reduction  of,  from  its  solution  by 

iron,  early  knowledge  of,  1 
removal  of  oxide  from,  158 
salts,  poisoning  by,  423 
scratch  brushes  for,  146 
sheet,  nickeling,  209 
silvering  of,  early  knowledge  of,  1 
Smee's  experiments  with,  353 
steel-gray  color  on,  407 
sulphate,  441,442 

solutions,  different, 
table  of  specific  elec- 
trical resistances  of, 
at  various  tempera- 
tures, 464 
to  coat  zinc  plates  with  a  very 

thin,  but  hard  layer  of,  236 
wire  and  plates,  weights  of,  474 
fine,  silvering  of,  280 
pure,  table  of  the  electrical 

resistance  of,  472 
-zinc   alloy,    solution   for    trans- 
ferring, 242,  243 

Coppered    art-castings,    inlaying   de- 
pressions of,  237,  238 
articles,  bronzing  of,  405 

coating    of,     with     another 

metal,  235 

turning  white  of,  234,  235 
Coppering,  225-238 

by  contact  and  dipping,  235,  236 
cleansing  of  articles  previous  to, 

232,  233 

defective  places  in,  233 
execution  of,  231-235 
needles'  eyes,  237 
sheet  zinc,  206,  207 
small  articles,  en  masse,  235 

dark,  round  stains  in,  233, 

234 

steel  pens,  237 

Cork,  gilding  with  the,  310-312 
Corn-flower  blue  on  brass,  411 
Corvin's  niello,  398,  399 
Coulomb,  law  of,  15 

the,  31 

Counter  current,  27 
currents,  191,  192 
-shaft,  to  find  speed  of,  in  accord 
ance  with  main  shaft  and  ma- 
chine, 475 
Cream  of  tartar,  446 
Crucibles,  449 
Cruikshank's  investigations,  3 

trough  battery,  2 
Cubic  nitre,  444 
Cuivre  fume,  405 


Cuivre  poli  deposit,  238-247 
Cupric  sulphate,  441 ,  442 
Cupron,  copper  bath  with,  229 

element,  50 
Cuproso-cupric   sulphite,   brass   bath 

with,  241 
copper  baths  with, 

229 

Cuprous  sulphite,  442 
Cups,  gilding  the  inner  surfaces  of,  297 
Current,  counter,  27,  191,  192 

electric,  chemical  actions  of  the, 

25-31 
extra,  25 
galvanic,  16 
hydro-electric,  16 
induced,  24 
inductive,  24 
polarizing,  27,  192 
primary,  24 
quantity  for  the  correct  formation 

of  the  deposit,  91,  92 
of,  17-21 

coupling  elements  for,  20 
regulator,  93,  94 
secondary,  24 
sources  of,  32-84 

volumes,   table   of  the  value   of 
equal,  as  expressed  in  amperes 
per     square      decimetre,     per 
square  foot  and  per  square  inch 
of  electrode  surface,  463,  464 
Currents,  alternating,  25 
Cutlery,  cleansing  of,  269 
Cyanides,  4o5-438 

poisoning  by,  422,  423 

DANIELS  element,  35,  36 
for     galvanoplastic 

depositions,  360 

Dark  steel  gray  color  on  copper,  407 
Daub,  R.,  cobalt  bath  recommended 

by,  223, '224 
Davy,  Sir  H.,  discovery  of  potassium 

and  sodium  by,  3 
Dead  black  on  copper,  405,  406 

gilding,  299-301 

Deep  black  color  on  copper,  406 
Delval,    copper    bath    recommended 

by,  351 
Deposit,  cuivre  poli,  238-247 

detaching  the,  from  the  mould, 

380 

formation  of  the,  122,  123 
or  shell,  backing  the,  380-382 
penetration  of  the,  into  the  basis- 
metal,  167 
Deposition,  first  requisite  for,  91 


INDEX. 


483 


Deposition  of  antimony,  arsenic  and 
aluminium,    345-352 
cobalt,  221-225 
copper,       brass       and 

bronze,  225-248 
gold,  287-318 
nickel,  169-221 
nickel  and  cobalt,  169- 

225 

platinum     and     palla- 
dium, 318-326. 
silver,  249-287 
tin,  zinc,  lead  and  iron, 

326-345 

Deposits  of  iridium  and  rhodium,  326 
De  Ruolz,  first  deposition  of  metallic 

alloys  by,  6 
labors  of,  5 

Dip,  preparation  of,  153 
Dipping,  109 
basket,  193 
baths,  exhausted,  recovery  of  acid 

and  metal  from,  155,  156 
for  gilding  by,  308-310 
brassing  by,  247 
coppering  by,  235,  236 
Du  Fresne  s  method  of  fire-gilding,315 
Dun's  potash  element,  51,  52 
Dupre's   solution  for  filling  the  ele- 
ments, 40 
Dynamo,  best  mode   of  setting  the, 

in  motion,  110 
Brush,  70-72 
copper    bath   for   galvanoplastic 

depositions  with  the,  362 
-electric  machine,  definition  of  a, 

64 

parts  of  a,  64 
machines,      arrangements 

with,  109-121 
various,  8,  9 
evolution  of,  in  the  United  States, 

77-84 
Fein's,  70 

-generator,  parts  of  a,  64 
Gramme,  66,  67 

disadvantage  of,  68,  69 
Krottlinger,  74.  75 
I/ahmeyer,  75-77 
"Little  Wonder,"  78 
machines,  66 

galvanoplastic       depositions 

with  the,  361-367 
modern  Gramme,  67,  68 
most  suitable,  data  for,  84 
rules  for  setting  up  a,  109,  110 
Schuckert's  flat  ring,  69,  70 
Siemens  &  Halske,  72-74 


Dynamo,  stripping  nickeled  articles 

with  the,  196 
transition  of  the  magneto-electric 

machine  to  the,  65 
"Wonder,"  78,79 

Dynamos  manufactured  by  the  Han- 
son &  Van  Winkle  Co.,  77-84 
Dyne,  30 

T^BERMAYER,  experiments  of,  in 
JJ,  coloring  brass,  411,  412  , 

silver-immersion  bath,  accord- 
ing to,  274 

Electric  connection  gripper,  374,  375 
induction,  discovery  of,  4 
units,  30 
Electrical   current,  chemical  actions 

of  the,  25-31 
potential,  16 
Electricities,  attraction  and  repulsion 

of,  13 
Electricity,  12-21 

and  magnetism,  10-31 
double  fluid  hypothesis  of,  14 
Herz's  investigations  of  the  na- 
ture of,  15 
kinds  of,  13 
negative,  13 
positive,  13 
resinous,  13 

single  fluid  hypothesis  of,  14 
vitreous,  13 

Electro-chemical  and  chemical  equiv- 
alents, table  of,  462, 463 
equivalents,  29,  30 
processes,   prominent  in- 
vestigators  and  practi- 
tioners of,  9 

Storage  Battery  Co.,  plant 
installed  by  the,  378-380 
-chrorny,  339-341 
-deposition  by  contact,  168,  169 
combination    of   fire-gilding 

with,  314,  315 
imitation  of  niel  by,  282 
processes  of,  159-169 
upon  aluminium,  350-352 
-etching,  385-387 
-gilder,  brush  employed  by  the, 

126 

-gilding,  first  practical  results  at- 
tained in,  3 
-magnetic     induction     machine, 

first,  construction  of,  4 
-magnetism,  21-23 
-magnets,  23 

-metallurgy,  historical  review  of, 
1-9 


484 


INDEX. 


Electro-motive  force,  16 

of  elements,  table  of, 

465 

series  of,  15 
tension,  series  of,  15 
-plating  arrangements  in  partic- 
ular, 89-121 

chemical  products  and  vari- 
ous apparatus  and   instru- 
ments used  in,  424-453 
establishment,   ground  plan 

of  an,  116-120 
establishments,  arrangement 

of,  in  general,  85-1 2l 
plant,  parts  of  a,  89 
Electrodes,  26 
Electrolysis,  25-31 

decomposition  of  water  by,  3 
Electrolyte,  26 

Electrolytic  laws  discovered  by  Fara- 
day, 27-29 
Electropoion,  40 
Electrotypes   in    iron,    bath   for  the 

production  of,  342 
finishing,  382-385 
nickeling,  214-216 
Element,  Becquerel's,  35 
Bunsen,  37-40 
cupron,  50 
Daniell's,  35,  36 
Dun's  potash,  51.  52 
galvanic,  16 
Grove's,  37 

Knaffe  and  Kiefer's,  52 
Lallande  and  Chaperon,  48-50 
Leclanche,  48 
Meidinger,  36.  37 
Oppermanu's,  44-48 
Smee's,  34,  35 

Elements,  arrangement  with,  89-109 
Buusen,  location  of,  86 

manipulation  of,  42,  43 
constant,  35 
coupling  of,  19,'20 

for  electro  motive  force 

or  tension,  20 
quantity  of  current, 

20 
determination  of  the  number  of, 

required  for  plating,  90,  91 
Dupre's  solution  for  filling  the,  40 
galvanic,  o2-57 
mixed  coupling  of,  20 
soluble    chromium    combination 

for,  41 
table  of  the  electro-motive  force 

of,  465 
various,  51 


Elements,  with  their  symbols,  atomic 
weights  and  specific  gravities, 
table  of,  461 

Elkington    establishment,    Birming- 
ham, arrangement  in  the,  for 
agitating  the  silver  bath,  257 
observations  of,  258 
Elkingtons,  labors  of  the,  5 
Eisner's  bronze  bath,  247 

tinning  bath,  332 

Endless  belt  machine  or  belt  strap- 
ping attachment,  142,  143 
Emery,  grades  of,  132 
Etching  ground,  386 
Evaporating  dishes  or  capsules,  448 
Exhaust  tumbling  barrel,  129,  130 
Eyes,  silvering  of,  275 

tinning  solution  for,  331,  332 

•PAHRENHEIT,     Centigrade     and 
JP     Reaumur    thermometers,    com- 
parison of  the  scales  of  the,  and 

rules   for   converting   one   scale 

into  another,  476 

Faraday,  discovery  of  electric  induc- 
tion by,  4 

electrolv  tic   laws  discovered  by, 

27-29 

Farad,  the,  31 
Fein's  bichromate  battery,  53,  54 

dynamo,  70 
Ferric  oxide,  144 

sulphide,  431 
Ferrous  sulphate,  441 
Fibre  brushes,  135 
Fibres,  135 
Field,  magnetic,  12 

magnets,  the,  64 
Filtering  material,  451 
Filters,  451,  452 
Fine  wheel,  132 

Fire  gilder,  brush  employed  by  the, 
126 

gilding,    combination     of,    with 
electro-deposition,  314,  315 

or  mercury  gilding,  312-315 
Flasks  and  glass  balloons,  448 
Flexible  shaft,  143,  144 
Floors  of  plating  rooms,  best  material 

for,  87 

Flowers   coating  of,  with  copper,  399 
Force,  lines  of,  63 

or  power,  30 

region  of  the  lines  of,  63 
Foote  s  pinnacle  gravity  battery,  43, 

44 

Foot  lathe,  137-139 
Forks,  deposit  of  silver  on,  262 


INDEX. 


485 


Forks,  extra  heavy  coating  of  silver  on 

the  convex  surfaces  of,  270 
slinging  wires  for,  262 
French  form  of  cell  apparatus,  357 
Friction,  contact  and  immersion,  gild- 
ing by,  305-312 
gilding  by,  310-312 
Frosting,  swing  brushes  for,  123 

/^AIFFE,  recommendation  by,  222 
VjT     Galvani,    discovery    of    contact 

electricity  by,  1 
experiments  of,  1,2 
Galvanic  chain,  10 
current,  1(5 
element,  1G 
elements,  32-57 
.Galvanometer,  astatic,  22 

first  construction  of  the,  4 
horizontal,  95 
indications  by  the,  97-100 
sine,  22 
tangent,  22 
vertical,  95 
Galvanometers,  22 
Galvauoplastic   baths,    agitation     of, 

362-865 
anodes  for,  365 
determination    of 
content  of  cop- 
per in,  366,  367 
determination    of 
free     acid     in, 
365,  366 
deposit,  current  strength  for,  376, 

377 

deposition    by   the    battery   and 
dynamo  machine,  359- 
367 
in    the    cell    apparatus, 

354-359 

depositions,  copper  baths  for, 
with  a  separate  source 
of  current,  361-365 
of  copper,  elasticity, 
strength  and  hardness 
of,  362 

method  for  originals  in  high  re- 
lief, 396 
operations  in  iron,  400,  401 

nickel,  401,  402 
silver  and  gold,  402, 

403 
operator,    pencils    and    brushes 

used  by  the,  126 
process,  invention  of  the,  4 
reproduction  of  busts,  vases,  etc., 
388,  389 


Galvanoplasty,  352-403 
definition  of,  352 
processes  used  in,  353 
special  uses  of,  397-400 
Galvanoscope,    first    construction   of 

the,  4 

Galvanoscopes,  22 
Gas  carbon  anodes,  182 
Gassiot,    plan     to     obtain     metallo- 
chromes,  recommended  by,  340,341 
Gauduin's  copper  bath,  231 
Gauze,  metallic,  gilding  of,  303,  304 
Gelatine  moulds,  396,  397 
German  form  of  cell  apparatus,  357, 

358 

silver  articles,  stripping  of,  316 
deposit  of,  220,  221 
pickling  of,  151,  152 
polishing  of,  136 
preparation  of,  for  silvering, 

269 

removal  of  oxide  from,  158 
Germany,  process  for  the  determina- 
tion of  genuine  silvering  in  use 
by  custom-bouse  officers  in,  285 
Gilded  articles,  beautiful  rich  appear- 
ance of,  302 
matt  for,  308 
removing  gold  from,  315, 

316 

stripping,  315,  316 
Gilder  of  watch  works,  brush  used  bv 

the,  126 

Gilding,  bichromate  element  for,  55 
by  contact,  305-3(18 

immersion,  and  by  fric- 
tion, 305-312 

dipping,  baths  for,  308-310 
friction,  310-312 
weight,  297 

cold,  bath  for,  289,  290 
coloring  of,  301 .  302 
current-strength  for,  296,  297 
dead,  299-301 

defective,  treatment  of,  308 
execution  of,  295-298 
fire  or  mercury,  312-315 
genuine,   determination  of,    316, 

317 

glass,  310 
green,  299 
hot,  bath  for,  291 
improving  bad  tones  of,  302 
in  the  cold  bath,  process  of,  297 
porcelain,  310 

preparation  of  articles  for,  296 
red,  298,  299 
rose-color,  299 


486 


INDEX. 


Gilding,  wax,  301.  302 

with  the  cork.  310-312 

hot  bath,  297,  298 
rag,  310-312 
thumb,  310-312 
without  a  battery,  295,  296 
Glass  balloons  and  flasks,  448 
gilding,  310 
jars,  448,  449 
metallization  of,  400 
platinizing,  324 
Glauber's  salt,  440 
Glue  pot,  141,  142 
Gold  amalgam,  preparation  of,  312 
bath,  determination  of  the   con- 
tent  of  copper  in  a,   for  a 
beautiful  red  gold,  299 
with  yellow  prussiate  of  potash, 

290,  291 
baths,  288-293 

management  of,  293-295 
preparation  of,  with  the  assist- 
ance of  the  electric  current, 
292 

recovery  of  gold  from,  317,  318 
small,  porcelain  dish  for,  294. 

295 

baths,  vats  for,  294 
burnt,  300 
chloride,  434 
color,  pale,  on  brass,  409 

resembling,  on  brass,  409,  410 
deposit,  coloring  of  the,  293,  294 

redder  color  on,  301,  302 
deposition  of,  287-318 
deposits,  polishing,  149,  298 
galvanoplastic      operations     in, 

402,  403 

incrustations  with,  281 ,  303 
native,  analyses  of,  287 
occurrence  of,  287 
porcelain  capsules  for  dissolving, 

306,  307 

properties  of,  287,  288 
recovery    of,    from    gold    baths, 

317,318 
removing,    from   gilded  articles, 

315,  316 

scratch  brushes  for,  146 
solder,  table  of,  469 
varnishers,  operation  of,  419,  420 
-workers,  bichromate  element  for 

temporary  use  by,  55 
Gore,  brass  bath  recommended  by,  242 

experiments  of,  167 
Gountier's  bronze  bath,  247 
Goze's  process  for  obtaining  a  deposit 
of  aluminium,  348,  349 


Grained  surface,  production  of  a,  by 

pickling,  156 
Graining,  277-280 

operation  of,  279,  280 
preparations  used  for,  278,  279 
Gramme's  machine,  8,  60,  67 
Grasses,  coating  of,  with  copper,  399 
Gray  on  zinc,  413 

with  a  bluish  tint  on  brass,  409 
Grease,  freeing  the  objects  from,  108, 

109 

removal  of,  156-158 
table   for   freeing   articles  from, 

118,119 
Green  gilding,  299 

vitriol,  441 
Grinding,  132,  133 

disks,  construction  of,  132 

treatment  of,  133 
execution  of,  134 
flexible  shaft  for,  143,  144 
lathes,  133,  134 
rooms,  88 

Gripper,  electro-connection,  374,  375 
Grove's  element,  37 
Giilcher's  thermo  electric  pile,  60-62 
Gun-barrels,  browning  of,  347,  414 

coating  of,  with  lead,  339 
metal,  238 

Gutta-percha,  introduction  of,  5 
moulding  in,  367-369 
softening,  368 

HAEN,    determination   of  content 
of    copper    in     galvanoplastic 
baths,  according  to,  366,  367 
Hanson  &  Van  Winkle  Co.,  dynamos 
manufac- 
tured     by 
the,   77-84 
lathe  manu- 
factured 
by  the,  139, 
141 

plating  room 
arranged 
by  the,  120 

Hard  solder,  table  of,  468 
Hassauer's  copper  bath,  226. 
Hauck's  thermo-electric  pile,  59,  60 
Heat,  development  of,  in  the  conduc- 
tor, 29 

Hefner-Alteneck's  machine,  8 
Heliography,  387,  388 
Herz,  Prof.,  investigations  of,  15 
Hess,  bath  of,  for  deposits  of  tombac, 

248 
solution  for  transferring  any  cop- 


INDEX. 


UNIVEBSTT 


487 


per-zinc    alloy,    according    to, 
242,  243 
Hoe  &  Co.,  electro-connection  gripper 

of,  374,  375 

Hollow-ware,   Britannia,  preparation 

of,  for  silvering,  269,  270 

gilding  the  inner  surfaces 

of,  297 

Holmes  type  of  machine,  7,  8 
Hooks,  silvering  of,  275 

tinning  solution  for,  331,  332 
Horn  silver,  433,  434 
Horse-power,  English,  31 

French,  31 

Hot  gilding,  bath  for,  291 
Hiibl,  experiments  of,  on  the  elastic- 
ity, strength 
and  hardness 
of  galvano- 
plastic  deposi- 
tions of  cop- 
per, 362 

with  galvano- 
plastic  baths 
at  rest  or  in 
motion,  362, 
363 

with  copper,  353 
Hydraulic  press,  369,  370 
Hydrochlorate  of  zinc,  432,  433 
Hydrochloric  acid,  425,  426 
Hydrocyanate  of  silver,  437 

zinc,  437 
Hydrocyanic  acid,  426 

poisoning  by,  422, 423 
Hydro-electric  current,  16 
Hydrofluoric  acid,  428 
Hydrometers,  449-451 
Hydroplatinic  chloride,  434,  435 
Hydrosulphate  of  ammonia,  430 
Hydrosulphuric  acid,  429,  430 
Hygienic    rules    for    the  workshop, 

421-424 

Hyponitric  gases,  poisoning  by,  423, 
424 

TDIO-ELECTRICS,  13 

Immersion,  contact  and  friction, 

gilding  by,  305-312 
deposits  of  antimony  and  ar- 
senic by,  347.  348 
silvering  by,  271-277 
tinning  by,  330 
Incrustations  with  gold,  303 

silver,  gold,  and  other 

metals,  281 
Induced  current,  24 
Induction,  23-25 


Induction,  electric,  discovery  of,  4 
Inductive  current,  24 
Inductor  ring,  cleaning  of  the,  110,111 
Inlaying  brassed  articles,  247 

depressions  of  coppered  art  cast- 
ings, 237,  238 
Instruments  and  apparatus,  various, 

448-453 

sharp  surgical,  nickeling,  213, 214 
surgical,  coating  wooden  handles 

of,  with  copper,  400 
Ions,  26 
Iridescent  colors,  production  of,  339- 

341 

Iridium,  deposits  of,  326 
Iron-ammonium  sulphate,  441 
articles,  brightening  of,  131 
coating  of,  with  lead,  339 
grinding  of,  135,  136 
superficial  coating  of  tin  on, 

ooo 

tinning  solution  for,  331 

bath  for  brassing,  241 

baths,  management  of,  344 

blue  on,  416 

brown  black  with  bronze  lustre 
on,  416 

cast,  bath  for  brassing,  242 
coating  with  bronze,  247 
tinning  of,  328 
zinc  bath  for,  335 

castings,  unground,  brassing  of, 
246,  247 

coloring,  414-416 

copper  baths  for,  226,  227 

coppering  of,  previous  to  nickel- 
ing, 185,  186 

current  for  nickeling,  188 

deep  black  deposit  on,  343,  344 

deposition  of,  341-345 

electrotypes  in,  bath  for  the  pro- 
duction of,  342 

galvanoplastic  operations  in,  400, 
401 

lustrous  black  on,  414,  415 

nickel  bath  for,  178 

objects,    brassed,    bronze   Barbe- 
dienne  on,  410 

objects,  removal  of  oxide  from,  158 

ore,  magnetic,  10 

pickle  for,  151 

protosulphate,  441 

-sheet,  nickeling,  209,  210 

silvering  of,  early  knowledge  of,  1 

silvery     appearance    with     high 
lustre  on,  416 

sulphate,  441 

wire  and  plates,  weights  of,  474 


488 


INDEX. 


Iron,  wrought,  bath  for  brassing,  242 
coating  with  bronze,  247 
zinc  bath  for,  335 
zinckiug  of,  by  contact,  337 

ACOBY,    Prof.,    invention    of   the 

galvanoplastic  process  by,  4.  5 
Joule's  experiments,  1:9 


J 


KAISER,  R.,  deposition  of  an  alloy 
containing  nickel  according  to, 
219 

Kaselowsky's  nickel  bath,  176 
Keiser  &  Schmidt's  bichromate  bat- 
tery, 54 

Kettles,  164.  lf>5 

Klein,  steel  bath  recommended  by,  342 
Knaffe  and  Kiefer's  element,  52 
Knife  blades,  nickeling,  213,  214 
Knight,  S.  P.,  wet  process  of  black 

leading  invented  by,  372 
Knives,  deposit  of  silver  on,  262 
Kristaline,  418 
Krottlinger  dynamo,  74,  75 

T  ACES,  coating  of,  with  copper,  398 
\^f     Lacquer  similar  to  zapon,  prep 

aration  of,  418,  419 
Lacquering,  417-420 
Lacquers    and    varnishes,    cellulose, 

417-419 

Lahmeyer  dynamo,  75-77 
Lallande  and  Chaperon  element,  48- 

50 
Lamp-feet  of  cast-zinc,  nickeling  of, 

190, 191 

legs,  brassed,  coloring  gray,  346 
Lang  &  Son,  patent  of  for  nickeling 

wire  gauze  212.  213 
Langbein     Dr.    G.,    plunge    battery 

manufactured  by,  56,  57 
Lathe  brush,  147,  148 
foot,  137,  138,  139 
manufactured  by  the  Hanson  & 

Van  Winkle  Co.,  139,  141 
Lathes,  American  double  polishing, 

139 

grinding,  133,  134 
Law,  Coulomb's,  15 
Ohm's,  4,  17,  18 

Laws,  electrolytic,  discovered  by  Far- 
aday, 27-29 
Lead  acetate,  447,  448 
baths,  338 

deposition  of,  338-341 
properties  of,  338 
removal  of  oxide  from,  158 
salts,  poisoning  by,  423 


Leading  by  contact,  339 

Leather,  plates  for  the  production  of 
imitations  of,  399 

Leaves,  coating  of,  with  copper,  399 

Leclanche  element,  48 

Lenoir's  process  —  galvanoplastic 
method  for  originals  in  high  relief, 
396 

Lime,  burnt  or  quick,  429 

mixture  preparation  of,  157 
neutralization  of  the  effect  of,  421 

Line,  neutral,  10 

Lines  of  force,  63 

"  Little  Wonder  "  dynamo,  78 

Liver  of  sulphur,  430 

Loadstone,  10 

London  Metallurgical  Co.,  areas  sil- 
vering patented  by,  259 

Liidersdorff,  solution  for  coppering 
by  contact  given  by,  2^5,  236 

Lunar  caustic,  445, 446 

Lustrous  black  on  brass,  408 

Lyes,  caustic,  neutralization  of  the 
effect  of,  421 

MACHINE,  to  find  the  speed  of  a, 
475,  476 

Magnetic  field,  12,  63 
iron  ore,  10 
meridian,  11 
needle,  deflection  of  the,  by  the 

electric  current,  3 
rule  for  the  determination  of 
the  direction  of  the,  to  the 
conducting  wire,  21 
poles,  10 
Magnetism,  10-12 

Ampere's  theory  or  hypothesis 

of,  11,  12 

and  electricity,  10-31 
Magneto-   and    d\  namo-electric   ma- 
chines, 62-84 
-electric   machine,    transition   of 

the,  to  the  dynamo,  65 
machines,  66 

Manduit,  bronzing  copper  and  cop- 
pered articles  according  to,  405 
Manne.cmann    Pipe    Works,    process 
of  the,  for  electro-deposition  upon 
aluminium,  352 
Marble,  4h9 

Martin  and  Peyraud,  method  of  gild- 
ing by  friction,  described  by,  311, 
312 

Matrices  in  plastic  material,  prepara- 
tion of,  367-371 

Medals,  cell  apparatus  for  moulding, 
355 


INDEX. 


489 


Medals,  taking  casts  from,  390,  391 
Medium  wheel,  132 
Meidinger  element,  36,  37 
Mercuric  nitrate,  445 
Mercurous  nitrate,  444,  445 
Mercury  or  fire  gilding,  312-315 

salts,  poisoning  by,  423 
Meriden  Britannia  Co. ,  practice  of  the, 
in  preparing  ar- 
ticles for  silver- 
ing, 208,  269 
solution  for  silver 
plating  used  by 
the,  270 
striking    solution 

of  the,  270 

Meridian,  magnetic,  11 
Meritens,  bright  black  color  on  iron  I 

according  to,  415 
Metal,  recovery  of,  from   exhausted 

dipping  baths,  155,  156 
white,  preparation  of,  for  silver- 
ing, 268,  269 
Metallic  articles,  chemical  treatment 

of,  150-159 
mechanical  treatment  of, 

122-150 
treatment  of,  122-159 

before  elec- 
tro plating, 
122-145 
during  and 
after  the 
electroplat- 
ing process, 
145-150 

chromes,  330-341 
to}S,    metallo  chromy   for   orna- 
menting, 341 
wire  and  gauze,  gilding  of,  303- 

305 
Metallization  by  metallic  powders,  395 

the  wet  way,  393-395 
Metals,  coloring,    patiniziug,  oxidiz- 
ing of,  403-417 
conductivity  of,  17 
incrustations  with,  281 
reduction  of,  without  a  battery, 

168, 169 
table  of  melting  points  of  some, 

469 

Moire",  metallique,  326 
Molecules,  Clausius's  theory  of,  26,  27 
Monopotassic  carbonate,  438 
Montgomery,    Dr.,   introduction   by, 

of  gutta-percha,  5 

Mould,  detaching  the   deposit  from 
the,  380 


Moulding  in  gutta-percha,  367-369 

plaster  of  Paris,  391,  392 
in  wax,  370,  371 
Moulds,  gelatine,  396.  397 

in   plastic   material,    preparation 

of,  367-371 
metallic  alloys  for  preparing,  389, 

390 
metallizing  of,  by  the  wet  wayt 

393-395 

metallization  of,  by  metallic  pow- 
ders, 895 

suspension  of,  in  the  bath,  375 
Multipliers,  22 
Muriate  of  gold,  434 

zinc,  432,  433 
Muriatic  acid,  425,  426 
Murray,  discovery  by,  of  making  non- 
metallic  surfaces  conductive,  5 

\TATURE-PRINTING,  397.  398 
|\      Needles'  e)es,  coppering,  237 

tinning  of,  332.  333 
Nees,  Prof.,  process  of,  for  electro- 
deposition  upon  aluminium,  351,352 
Negative  wire,  103 
Neutral  line,  10 

zone,  10 

Nicholson   and   Carlisle,  decomposi- 
tion of  water  by,  3 
Nickel  alloys,  deposits  of,  219-221 
-ammonium  sulphate,  443 
and  cobalt,  deposition  of,  169-225 
anodes,  180-184 

reddish  tinge  of,  184 
rolled,  183 

articles,  preparation  of,  for  silver- 
ing, 269 

bath,  alkaline,  testing  of,  184 
electro  itotive  force  required 

for  a,  90 

English,  formula  for,  179 
for  rough  or  polished   cast- 
ings, 179 

small  articles,  179 
.   very  thick  deposits,  179, 

180 

most  simple,  173 
neutral,  172 
suspension  of  articles  in  the, 

186 

without  nickel  salt,  180 
baths,  170-180 

addition  of  bisulphide  of  car- 
bon to,  179 
anodes  for,  181 
containing  boric  acid, 175-177 
current  strength  for,  186, 187 


490 


INDEX. 


Nickel  baths,  determination  of  acidity 

and  alkalinity  of,  172,  173 
for  special  purposes,  178,  179 
freshly  prepared,  working  of, 

180 
old,  recovery  of  nickel  from, 

216,  217 

preparation  of,  165 
refreshing,  198,  199 
use  of  carbon  anodes  in,  182 
rolled  and  cast  anodes  in, 

183 

vats  for,  104,  105 
bronze,  220 
carbonate,  440 
chemical  equivalent  of,  170 
chloride,  433 

-copper-tin  alloy,  bath  for  depos- 
iting, 220 

-zinc  alloy,  solution  for  de- 
positing, 220 
deposition  of,  169-221 

from  its  double  salt,  6 
deposits,  dead,  199 

polishing,  149,  199 
galvanoplastic  operations  in,  401, 

402 

harder  and  more  brittle,  deposi- 
tion of,  172 

patent  for  the  deposition  of,  6 
properties  of,  169,  170 
recovery  of,  from  old  baths,  216, 

217 

scratch  brushes  for,  146 
silver,  preparation  of,  for  silver- 
ing, 269 

sulphate,  442,  443 
various  colors  upon,  407,  408 
very  thick  deposits  of,  189 
Nickeled  articles,  stripping  of,  194-196 
objects,     removal     of     moisture 

from,  148 

Nickeling,  additional  rules  for,  191 
bath,  slightly  acid  reaction  of,  171 
baths,  additions  to,  171,  172 
black,  344 
brass  sheet,  209 

by  contact  and  boiling,  217-219 
change  of  color  of,  197 
copper  sheet,  209 
criteria  for  judging  the  correct 

progress  of,  187,  188 
dark,  or  spotted,  or  marbled,  196, 

197 

defective,  to  improve,  217 
discolored,  196 

electrotypes,    cliches,    etc.,    214- 
216 


Nickeling,    en   masse   of   small   and 

cheap  objects,  193,  194 
knife   blades,   sharp  surgical  in- 
struments, etc.,  213,  214 
partial,  cause  of,  190 
peeling   of,  in    scratch-brushing, 

197 

polarizing  phenomena  in,  191-193 
process  of,  184-193 
remedy    against     the    yellowish 

tone  of,  196 

resume  of  the  principal  phenom- 
ena which  may  occur  in,  196- 
198 

salts,  prepared,  171 
sheet  iron,  209,  210 
-steel,  209,  210 
zinc,  199-209 
small  holes  in,  198 
solid,  189 

sufficiently  heavy,  test  for,  189 
suspension  of  objects  in,  190 
tin-plate,  209 
use  of  hand  anode  in,  190 
wire,  210-212 

gauze,  212,  213 

with  too  strong  a  current,  187 
yellowistutinge  of,  197 
Nickelous  cyanide  solution,  addition 

of,  to  silver  baths,  259 
Niel,  imitation  of,  281,  282 
Nielled,  silvering,  imitation  of,  281, 

282 

Nielling  powder,  281 ,  282 
Niello,  Corvin's,  398,  399 
Nitrates,  444-446 
Nitre,  444 
Nitric  acid,  425 

table  of  the   specific  gravity 

and  content  of,  471 
Nitrous  gases,  poisoning  by,  423,  424 
Nobili,  discovery  of  the  production  of 

iridescent  colors  by,  4 
Nobili 's  rings,  339-341 
Noe's  thermo-electric  pile,  58 
Non-electrics,  13 

Norris  and  Johnson,   brass  bath  ac- 
cording to,  242 
North  pole,  11 

fABERNETTER,     C.,     method     of 
\/     steeling  copper  printing  plates, 

employed  by,  342,  343 
Object  wire,  103 

coupling  the,  with  the   re- 
sistance boards,  voltmeter, 
shunt  and  baths,  114 
Object  wires,  insulation  of,  111 


INDEX. 


491 


Oersted,  Prof.,  discoveries  of,  3,  4 
Ohm,  law  of,  4,  17,  18 

the,  31 
Ohm's  law,  proposition  deduced  from, 

21 

useful  applications  of,  18-21 
Oil  of  vitriol,  424,  425 
Old  silvering,  282,  283 
Oppermann's  element,  44-48 
Organic  acids,  salts  of  the,  446-448 
Orpiment,  431 
Over-nickeling,  187 
Oxalate  solution,  preparation  of,  321, 

322 

Oxidized  silver,  283 
Oxidizing,     patinizing,    coloring     of 

metals,  403-417 

T)ACINOTTI,  invention  by,  of  the 
ring  named  after  him,  8 
ring  conductor  of,  65 
Painter's  gold,  288 
Palladium  baths,  325 

deposition  of,  325,  326 
properties  of,  325 
Pans,  boiling,  164,  165 
Paracelsus,  silvering  of  copper   and 

iron  known  to,  1 

Paris  Mint,  method  in  the,  for  pro- 
ducing brown  color  on  copper,  404, 
405 
Parkes's  method  of  metallizing  by  the 

wet  way,  394 

Paste,  cold  silvering  with,  277 
Pastes,  argentiferous,  composition  of, 

277 
Patina,  bluish,  407 

bronze-like  on  tin,  416 
brown,  on  cast  zinc,  414 
definition  of,  403 
genuine,  imitation  of,  406,  407 
green,  406 
Patinizing,     oxidizing,     coloring    of 

metals,  403-417 
Pfanhauser,  brass  bath  recommended 

by,  243 

copper  bath  according  to,  230, 231 
tin  bath  according  to,  328 
Philadelphia   Public   Buildings,  pro- 
cess employed  for  coating  the  col- 
umns of,  with  aluminium,  350 
Philipp's  process  of  coating  laces  and 

tissues  with  copper,  398 
Phosphates  and  pyrophosphates,  446 
Pickle,  preliminary,  152 
Pickles,  recovery  of  gold  from,  318 
Pickling,  109,  150-156 
duration  of,  151 


Pickling,  manipulation  of,  153,  154 
production  of  a  grained  surface 

by,  156 

Pile  of  Volta,  2 
Piles,  thermo-electric,  57-62 
Pilet,  palladium   bath  recommended 

by,  325,  326 
Pins,  nickeling  of,  193 
silvering  of,  275 
tinning  solution  for,  331 ,  332 
Pitchers,  gilding   the   inner  surfaces 

of,  297 
Pixii,  first  attempt  made  by,  to  devise 

an  electrical  machine,  65 
electro-magnetic       machine 

constructed  by,  4 

Plaster  of  Paris,   making  of,  imper- 
vious to  fluids,  392,  393 
moulding  in,  391,  392 
use  of,  for  casts,  390-393 
Plastic      material,      preparation      of 

moulds  in,  367-371 

Plater's  lathe  goblet  scratch  brush, 123 
Plates,  printing,  in  relief,  preparation 

of,  386,  387 
Plating  balance,  263-266 

-room  arranged  by  the  Hanson  & 

Van  Winkle  Co.,  120 
location  of  Bunsen  elements 

in,  86 
-rooms,  best   material   for  floors 

of,  87 

light  and  air  in,  85 
provision  for  heating,  86 
renewal  of  water  in,  87 
size  of,  87,  88 
sectional,  270 

solutions,  temperature  of,  86 
Platinic  chloride,  434,  435 
Platinizing  by  contact,  324 
execution  of,  323,  324 
glass,  324 
Platinum  anodes,  293 

insoluble,  in  silvering,253 
baths,  319-322 

management  of,  322,  323 
black,  318,  319 
deposition  of,  318-325 
deposits,  polishing  of,  149 
oxalate  solution,  preparation  of, 

321,  322 
phosphate   bath,  preparation  of, 

322 

properties  of,  318 
recovery  of,  from  platinum  solu- 
tions, 324,  325 

Platoso-ammonium   chloride,    prepa- 
ration of,  319,  320 


492 


INDEX. 


Plunge  batteries,  53-57 
Poisoning  by  alkalies,  423 
arsenic,  423 

chlorine,  sulphurous  acid, 
nitrous  and  hyponitric 
gases,  423,  424 
copper  salts,  423 
hydrocyanic         (prussic) 
acid,    potassium    cyan- 
ide, or  cyanides,  422.423 
lead  salts,"  423 
mercury  salts,  423 
sulphuretted     hydrogen, 

423 

Polarization,  34 
Polarizing  current,  27,  192 

phenomena,  191-193 
Pole,  north,  11 
pieces,  the,  64 
south,  11 
Poles,  attraction  and  repulsion  of,  11 

magnetic,  10 
Polishing,  137 
bobs,  137 

flexible  shaft  for,  143,  144 
lathes,  American  double,  139 
machines,  location  of,  88 

self-acting,  202 
materials,  144 
rooms,  88 

dust  in,  88,  89 
silvered  articles,  267 
wheels,  compress,  137,  138 
Poole,  M.,   first  use  of  thermo-elec- 
tricity by,  6 
Porcelain  gilding,  310 

metallization  of,  400 
Positive  wire,  103 
Potash,  438 

alum,  440,  441 
caustic,  428 
element,  Dun's,  51,  52 
yellow  prussiate  of,  437,  438 
white  prussiate  of,  435,  436 
Potassium  and  sodium,  production  of 

the  amalgams  of,  4 
bitartrate,  446 
carbonate,  438 

solutions  of,  table  of  the 
specific  gravity  and  con- 
tent of,  469 
cyanide,  160,  435,  436 

addition  of,  to   silver  baths, 

253,  254 

determination  of  proper  pro- 
portion of,  and  silver  in  a 
silver  bath,  256,  257 
handling  of,  422 


Potassium  cyanide,  holders  for  baths 

containing,  105 
poisoning  by,  422,  423 
proportion  of,  to   fine 
silver  in  silver  baths, 
252 
solutions,  introduction 

of  the  use  of,  5,  6 
use  of,  as  a  pickle,  152 
with    a   different   con- 
tent, table  of,  436 
discovery  of,  3 
ferro  cyanide,  437,  438 
hydrate,  428 
nitrate,  444 
sodium  tartrate,  447 
stannate,  preparation  of,  332 
sulphide,  430 
Potential,  electrical,  16 

or  electro-motive  force,  30 
Power,    consumption     of,     in     elec- 
trolysis, £0,  31 
or  force,  30 

Pretsch,     heliographic     process     in- 
vented by,  387 
Primary  current,  24 
Prime  &  Son,  perfection  by,   of  the 

invention  of  depositing  metals,  7 
Printing  plates  in  relief,  preparation; 

of,  386,  387 

Properties  of  silver,  249 
Prussiate  of  silver,  437 

zinc,  437 
Prussic  acid,  426 

poisoning  by,  422,  423 
Pulley  on  counter-shaft  carrying  belt 
to  machine,  to  find  diame- 
ter of,  475 
main  shaft,  to  find  diameter 

of,  475 
Pyrophosphates  and  phosphates,  446 

QUANTITY,  30 
Quicking,  261 

RAG,  gilding  with  the,  310-312 
Rain  water,  159,  160 
Ratsbane,  427 

Rauber's  sheet  grinding  and  polish- 
ing machine,  1102-20  4 
Reaumur,  Centigrade  and  Fahrenheit 
thermometers,    comparison    of  the 
scales  of  the,  and  rules  for  convert- 
ing one  scale  into  another,  476 
Recovery   of  silver  from    old   silver 

baths,  285-287 

Red  brown  color  on  copper,  405 
zinc,  414 


INDEX. 


493 


Red  gilding,  298,  299 

sulphide  of  antimony,  430 
Reduction  of  metals  without  a  bat- 
tery, 168,  169 

Region  of  the  lines  of  force,  63 
Reinbold,  H.,  formula  for  aluminium 

bath  by,  349 
Reliefs,  cell  apparatus  for  moulding, 

355 

Reproduction,  352-403 
Resist,  composition  of,  279,  280 
Resistance,  16,  17,  30 
board,  93,  94 

conditions     upon    which    its 

action  is  based,  94.  95 
Rheostat,  93,  94 

improved,  96,  97 
Rhodium,  deposits  of,  326 
Rinsing  apparatus,  108 
Rivets,  nickeling  of,  193 
Rochelle  salt,  447 
Rock  salt,  431 

Rogers  Manufacturing  Co.,  amount  of 
silver  upon 
plated  ware, 
manufac- 
tured by 
the,  262,  263 
methods  in 
use  b)r  the, 
for  prepar- 
ing work  for 
platiug,269, 
270 

solution  for 
silver  plat- 
ing used  by 
the,  270 
striking  solu- 
tion of  the. 
270 

Rose-color  gilding,  299 
Roseleur,    brass   bath   according   to,  I 

239,  240 
plating    balance,    improved    by, 

263-266 
Rouge,  144 
Roughing  wheel,  132 
Ruolz's  bronze  bath,  247 
Russia  gold,  composition  of,  287 

SAL  AMMONIAC,  431 
solutions,    table    of 
the  specific  grav- 
ity of,  471 
Salt,  common,  431 

rock,  431 
Saltpetre,  444 


Salts  of  the  organic  acids,  446-448 
Salzede's  bronze  bath,  247 

use  of,  for  tinning 

cast  iron,  328 
Sandblast,  126-128 
Satin  finish,  swing  brushes  for,  123 
Sawdust,  148 
Saw  table,  382 
Saxton,  electric  generator   produced 

by,  65 

Scamoni,    heliographic    process    im- 
proved by,  387 
Schuckert's  flat  ring  dynamo,  69,  70 

machine,  8 

Scouring,  brush  for,  126 
Scratch-brush,  hand,  mode  of  using 

the,  146,  147 

-brushes,  circular,  124,  125 
treatment  of,  124 
various  forms  of,  123 
-brushing,  123,  145-148 

decoctions  used  in,  146 
operation  of,  124 
Secondary  current,  24 
Sectional  plating,  270 
Seebeck,  Prof.,  discovery  of  a   new 

source  of  electricity  by,  57 
Seignette  salt,  447 
Sepia-brown   tone   upon   tin  and   its 

alloys,  416 

Shaft,  flexible,  143,  144 
Shaving  machine,  types  of,  382,  383 
Sheet  grinding    and    polishing  ma- 
chine, Rauber's,  202-204 
iron,  galvanized,  350 

plated  with  aluminium,  350 
Shell  gold,  288 

or  deposit,  backing  the,  380-382 
Shultz,  O.,  patent  of,  for  removing 
hydrochloric  acid  from   the   pores 
of  coppered  articles,  234 
Shunt,  the,  114 

Siemens,  Dr.  W.,  discovery  by,  65,  66 
first  machine  of,  8 
improvement  in   elec- 
tric generators  made 
by,  65 

&  Halske  dynamos,  8,  72-74 
Silver,    amount  of,    deposited    upon 
plated  ware,  manufactured  by 
the  Wm.  Rogers  Co.,  262,  263 
anodes,  251-260 
articles,  stripping  of,  316 
bath,  agitation  of,  257,  258 

determination  of  proper  pro- 
portions of  silver  and  potas- 
sium cyanide  in  a,  256, 
257 


494 


INDEX. 


Silver  bath,  for  ordinary  electro  silver- 
ing, 251 

with  silver  chloride,  prepara- 
tion of,  249,  2nO 
cyanide,  preparation 

of,  250,  251 
baths,  249-251 

addition  of  certain  substances 

to,  258 
potassium  cyanide 

to,  253,  254 
solution  of  nickel- 
ous    cyanide  in 
potassium  cyan- 
ide to,  259 
augmentation    of   silver    in, 

254-256 

current-strength  for,  252 
old,  recovery  of  silver  from, 

285-287 

prepared  with  chloride  of  sil- 
ver, life  of,  254,  255 
thickening  of,  255 
treatment  of,  251-260 
vats  for,  251 
chloride,  433,  434 

preparation   of  silver    bath, 

with,  249,  250 
coloring,  417 

control  of  the  weight  of  the  de- 
posit of,  263 
cyanide,  437 

preparation  of,  251 
deposition  of,  249-287 
deposits,  polishing  of,  149 
extra  heavy  coating   of,  on   the 
convex  surfaces  of  spoons  and 
forks,  270 
fine,  proportion  of,  to  potassium 

cyanide  in  silver  baths,  252 
foot  lathe  for  polishing,  138,  139 
galvanoplastic  operations  in,  402, 

403 

-immersion  bath,  274 
incrustations  with,  281 
nitrate,  445,  446 

of,  solution  of,  in  sodium  sul- 
phide, 272 
oxidized,  283 
plate,   foot  lathe   for  polishing, 

138,  139 
recovery  of,  from  old  silver  baths, 

285-287 

scratch-brushes  for,  146 
solder,  table  of,  468 
solutions    containing    potassium 
cyanide,  precipitation  of  silver 
from,  286,  287 


Silvered  articles,  burnishing  of,  267. 

268 

polishing  of,  267 
stripping  of,  283,  284 
yellow  color  on,  283 
Silvering,  amalgamating  articles  for, 

261 

antique,  282,  283 
areas,  259,  260 
bichromate  element  for,  55 
by   contact,   by   immersion,  and 
cold   silvering  with  paste, 
271-277 

weight,  260-268 
cold,  with  paste,  277 
coppering  previous  to,  268 
current-density  for,  92 
electro-deposited,    determination 

of,  284,  285 
elements  for,  252 
execution  of,  260-271 
fine  copper  wire,  280 
freeing  from  grease  for,  261 
in  contact  with  zinc,  bath  for,  271 , 

272 

insoluble  platinum  anodes  in,  253 
Meriden  Britannia  Co.'s  solution 

for,  270 

methods  in  use   by  the   Rogers 
Manufacturing  Co.  for  prepar- 
ing work  for,  269,  270 
nielled,  imitation  of,  281,  282 
old,  282,  283 
ordinary,  268-271 
bath  for,  251 
pickling  for,  261 

practice  of  the  Meriden  Britannia 
Co.  in  preparing  articles  for, 
268,  269 

preparation  of  Britannia  hollow- 
ware  for,  269. 
270 
metal    for,    269, 

270 
nickel    silver  for, 

269 

Rogers  Manufacturing  Co.'s  solu- 
tion for,  270 

scratch-brushing,  during,  262 
singular  phenomenon  in,  258 
yellow  tone  of,  258 
Similor,  238 
Sine  galvanometer,  22 
Siphons,  452,  453 

Skates,  removal  of  grease  from,  157 
Slinging  wires,  108,  262 
Smee,  A.,  discoveries  of,  6 

experiments  of,  with  copper,  353 


INDEX. 


495 


Smee's  element,  34,  35 

Smoke-bronze,  411 

Soda,  caustic,  428 

Sodium  and  potassium,  production  of 

the  amalgams  of,  4 
bicarbonate,  439 
bisulphite,  444 
carbonate,  438,  439 
chloride,  431 
citrate,  448 
discovery  of,  3 
hydrate,  428 
nitrate,  444 
phosphate,  446 
pyrophosphate,  446 
sulphate,  440 
sulphide,  preparation  of  solution 

of,  272-274 

sulphite,  160,161,  443,444 
Soft  solder,  table  of,  468 
Solder,  gold,  table  of,  469 
hard,  table  of,  468 
silver,  table  of,  468 
soft,  table  of,  468 

Solders  and  most  usual  alloys,  table 
showing  the  composition  of, 
466-469 

table  of.  468,  469 
Soldering  fluid,  380 
Solenoid,  the,  12 
Solubility  of  various  substances,  table 

showing  the,  466 
South  pole,  1 1 

Spaeth,  J.  W.,  machine  of,  for  gild- 
ing metallic  wire  and  gauze,  303, 304 
Speed,  rules  for,  475,  476 
Spencer,  T.,  claim  of,  to  the  inven- 
tion of  the  galvanoplastic  process,  5 
Spirit  of  hartshorn,  429 
Spirit  of  nitre,  425 
Spoons,  deposit  of  silver  on,  262 

extra  heavy  coating  of  silver  on 

the  convex  surfaces  of,  270 
German   silver,    preparation    of, 

for  silvering,  269 
nickel  silver,  preparation  of,  for 

silvering,  269 
slinging  wires  for,  262 
Spring  water,  constituents  of,  159 
Stannic  chloride,  432 
Stannous  chloride,  432 
Stearine,  moulding  in,  370,  371 
Steel  articles,  brightening  of,  131 

coating  of,  with  lead,  339 
co baiting,  223,  224 
grinding  of,  136 
preparation   of,  for  silver- 
ing, 269 


Steel  articles,  tinning  solution  for,  331 
Steel,  bath  for  brassing,  242 
baths,  341-344 
blue  on,  416 

copper  baths  for,  226,  227 
coppering  of,  previous  to  nickel- 
ing, 185,  186 

current  for  nickeling,  188 
direct  gilding,  bath  for,  291,  292 
gray  color  on  copper,  407 

on  brass,  408,  409 
objects,  removal  of  oxide  from, 158 

thin  film  of  copper  on,  237 
pens,  coppering,  237 
plates,  use  of,  in  place  of  silver 

anodes,  253 

sheet,  nickeling,  209,  210 
spring  carboy  rocker,  158,  159 
zinc  bath  for,  335 
Steeling,  341-345 
by  contact,  345 
execution  of,  344 
Stirring  rods,  453 
Stoehrer's  battery,  56 
Stolba,  method  of  tinning  according 

to,  333 

Stolba's  process  for  nickeling  by  con- 
tact, 217-219 
Stopping  off,  270,  271 

varnish,  271 
Storage     batteries,    electro-chemical 

process  of  forming,  378 
Straw  color,  to  brown  through  golden 
yellow,  and  tombac  color  on  brass, 
409 
Striking  solution,  268 

Meriden  Britannia  Co. 's, 

270 
Rogers     Manufacturing 

Co.'s,  270 
Stripping  acid,  195 

gilded  articles,  315,  316 
nickeled  articles,  194-196 
silvered  articles,  283,  284 
Sugar  of  lead,  447,  448 
Sulphates  and  sulphites,  440-444 
Sulphites  and  sulphates,  440-444 
Sulphur  combinations,  429-431 
Sulphuretted  hydrogen,  429,  430 

poisoning  by,  423 
Sulphuric  acid,  424,  425 

poisoning  by,  423,  424 
solutions,  different,  table 
of  specific  electrical  re- 
sistances of,  at  various 
temperatures,  464 
table  of  the  specific  grav- 
ity of,  470 


496 


INDEX. 


Sulphydrate  of  ammonia,  430 
Sulphydric  acid,  429,  430 
Surgical  instruments,  coating  wooden 
handles  of,  with  cop- 
per, 400 
sharp,  nickeling,  213, 

214 

Swing  brushes,  123 
Switch-board,  93,  94 

improved,  96,  97 


T 


ABLE  of  actual  diameters  in  dec 
imal  parts  of  an  inch 
corresponding  to  the 
numbers  of  various 
wire  gauges,  473 

approximate  content  of 
pure  crystallized  blue 
vitriol  at  different  de- 
grees Be.,  and  at  59° 
F.,  358 

chemical  and  electro- 
chemical equivalents, 
402,  403 

composition  of  the  most 
usual  alloys  and  sol- 
ders, 400-409 

electrical  resistance  of 
pure  copper  \vire  of 
various  diameters,  472 

electro-motive  force  of 
elements,  405 

elements  with  their  sym- 
bols, atomic  weights 
and  specific  gravities, 
401 

high  temperatures,  469 

melting  points  of  some 
metals,  409 

potassium  cyanide  with 
a  different  content,  430 

readings  of  different  hy- 
drometers, 450 

resistance  and  conductiv- 
ity of  pure  copper  at 
different  temperatures, 
472 

results  of  experiments 
with  galvanoplastic 
baths  at  rest  and  in 
motion,  303 

solubility  of  various  sub- 
stances, 400 

specific  electrical  resist- 
ances of  different  cop- 
per sulphate  solutions 
at  various  tempera- 
tures, 404 


Table  of  specific  electrical  resist- 
ances of  different  sul- 
phuric acid  solutions 
at  various  tempera- 
tures, 404 

specific  gravity  and  con- 
tent of  nitric  acid,  471 
specific  gravity  and  con- 
tent of  solutions  of  po- 
tassium carbonate,  409 
specific    gravity    of   sal 
ammoniac      solutions, 
471 

specific  gravity  of  sul- 
phuric acid,  470 
value  of  equal  current 
volumes  as  expressed 
in  amperes  per  square 
decimetre,  per  square 
foot  and  per  square 
inch  of  electrode  sur- 
face, 463,  404 
weights  of  iron,  copper, 
and  brass  wire  and 
plates,  474 

Tables,  useful,  401-470 
Tacony  Iron  &  Metal  Co.  of  Philadel- 
phia, process  used  by  the,  for  plat- 
ing the  columns  of  the  Philadelphia 
Public  Buildings,  350 
Tangent  galvanometer,  22 
Tanks,  103-105 

Bossard  Mechano- Electroplating, 

455-401 

Tartar  emetic,  447 
Taucher,  C.,  gold  bath  recommended 

by,  292 

tin  bath  according  to,328,329 
Temperatures,  high,  table  of,  409 
Terchloride  of  gold,  434 
Terra-cotta,  metallization  of,  4CO 
Thermo-electric  piles,  57-62 
electricity,  first  use  of,  0 
Thermometers,  coating  mercury  ves- 
sels of,  with  copper,  400 
Fahrenheit,  Centigrade  and  Re% 
aumur,  comparison  of  the  scales 
of  the,  and  rules  for  converting 
one  scale  into  another,  470 
Thompson,  S.  P.,  definition  of  a  dy- 
namo-electric machine  by,  04 
Thumb,  gilding  with  the,  310-312 
Tin  alloys,  sepia  brown  tone  upon,  410 
baths,  327-329 

current  strength  for,  329 
management  of,  329,  330 
bronze- like  patina  on,  416 
chloride,  432 


INDEX. 


497 


Tin,  coloring,  416 

dark  coloration  on,  416 

deposition  of,  326-833 

plate,  nickeling,  209 

properties  of,  326 

salt,  43^ 

sepia-brown  tone  upon,  416 
Tinning  by  contact  and  boiling,  330, 
331 

process  of,  330 

Tissues,  coating  of,  with  copper,  S98 
Toggle  press,  308,  369 
Tombac,  238 

deposits  of,  248 

pickling  of,  151,  152 

removal  of  oxide  from,  158 
Toys,   metallic,    metallo-chromy    for 

ornamenting,  341 
Tripoli,  144 
Trough  battery,  2,  32 
Tumbling  barrel,  exhaust,  129,  130 

dium,  128.  129 

operation  with  the,  130-132 
Twaddell's  hydrometer,  450 

T  TMBREIT  &  Matthes  element,  50 
U     United  States,  evolution  of  the 

dynamo  in  the,  77-84 
Units,  electric,  30 

VARNISH,    removal    of,    from    an 
imperfectly  varnished  object, 420 
Varnish,  stopping  off,  271 
Varnishes    and    lacquers,     cellulose, 

417-419 

for  gold  varnishers,  420 
Varreutrapp,  steel  bath  according  to, 

341 
Vases,  coloring  gray,  346 

galvanoplastic   reproduction    of, 

388,  38;) 
Vats,  103-105 

for  copper  baths,  231 
gold  baths,  294 
nickeling  sheet  zinc,  207 
silver  baths,  251 
Verdigris,  447 
Vienna  lime,  144 
Violet  on  brass,  411 
Vitriol,  blue,  441 ,  442 

table  of  approximate  con- 
tent of,  at  different  de- 
grees Be.,  and  at  59°  F., 
358 

green,  441 
oil  of,  424,  425 
white,  442 
Volt,  the,  3.1 

32 


Volta,  A.,  1 

pole  of,  2 
Voltaic  pile,  2 
Voltmeter,  114 

check,  454 

Weston,  100,  101 

WAHL,  Dr.  W.  H.,  directions  for 
preparing  platinum   baths  by, 
320-322 
Walenn,  copper  bath,  recommended 

by,  230 

Wales  gold,  composition  of,  287 
Warren,  cobalt  solution  described  by, 

223 

nickel  and   cobalt  solutions,  de- 
scribed by,  194 
Washing  soda,  438,  439 
Watch  movements,  plating  of,  with 

palladium,  325.  326 
parts,  grained,  gilding  of,  280 
Watches,    coloring  hands  and  dials 

of,  341 

Water,    decomposition    of,    by   elec- 
trolysis, 3 
importance  of,  159 
renewal  of,  in  plating  rooms,  87 
Watt,  the,  31 

Wax  mixtures  for  moulding,  370,  371 
mould,  preparation  of,  371 
moulding  in,  370,  371 
Weil,  copper  bath  of,  230 

zincking  according  to,  337 

and  Newton's  bronze  bath,  247, 

248 
Weiler,    L.,    conductivity  of   metals 

according  to,  17 
Well  water,  constituents  of,  159 
Weston  ammeter,  102 

boric  acid  as  an  addition  to  nick- 
eling baths  recommended  by, 
171,172 
dynamo,  77,  78 
nickel    bath    recommended    by, 

175,176 

voltmeter,  100,  101 
Wheatstone,  Sir  C  ,  discovery  by,  65, 

66 

Wheel,  fine,  132 
medium,  132 
roughing,  132 

Wheels,  compress  polishing,  137,  138 
White  arsenic,  427 

metal,  preparation  of,  for  silver- 
ing, 268,  269 

prussiate  of  potash,  435,  436 
vitriol,  442 
Whiting,  439 


498 


INDEX. 


Wire,   apparatus  for  nickeling,  211, 

212 

carriers,  special,  111 
gauze,  nickeling,  212,  213 
metallic,  gilding  of,  303-305 
nickeling,  2h:-^12 
Wires,  conducting,  103 

electrified,    general  law    of   the 

action  of,  23 
insulation  of,  103 
slinging,  108 

Wollaston,  discovery  by,  3 
"Wonder"  dynamo,  7S,  79 
Wood,  coating  of,  with  a  gal  van  o- 

plastic  deposit  of  copper,  31)9,  400 
Wooden  vats,  construction  of,  104 

lined  with  sheet  lead,  104, 

105 

Woolrych,    original    machine    con- 
structed by,  7 
Work,  30 
Workshop,    hygienic    rules   for  the, 

421-424 

Wright,  introduction  by,  of  the  use 

of  potassium  cyanide  solutions,  5,6 

Wrought  iron,  bath  for  brassing,  242 

coating  with  bronze,  247 

objects,  pickling  of,  150, 

151 
zinc  bath  for,  335 

VBLLOW-BROWN  shades  on  zinc, 
I  414 

prussiate  of  potash,  437,  438 

gold  bath  with, 
290,  291 

7APON,  417,418 

£j    Zilken,  solution  for  tinning  by 
contact  in  a  cold  bath,  patented 
by,  331 
Zinc  alloys,  337,  338 

amalgamation  of,  29,  33,  34 
articles,  copper  bath  for,  228 

polished,   slightly  coppered, 

nickel  bath  for,  178 
bath  for  brassing,  242 
baths,  334-336 

addition  of  salts  of  magne- 
sium  and    aluminium  to, 
335 
for  silvering  in  contact  with, 

271.272 
black  on,  413 
blue  black  on,  413 
bronzing  on,  413.  414 
carbonate,  439.  440 
cast,  brown  patina  on,  414 


Zinc,  cast,  nickeling  lamp-feet  of,  190, 

191 
castings,  nickel  bath  for,  178 

polishing  of,  136 
chloride,  160,  432,  433 

and  ammonium  chloride,  433 
coating  brass  with,  337 

copper  with,  337 
coloring.  413,  414 
coppering  of,  236 
current  for  nickeling,  188 
cyanide,  437 

dead  gilding  on,  300,  £01 
deposition  of,  333-338 
gray  coating  on,  413 
objects,    brassed,    bronze   Barb£- 

dienne  on,  410 
pickling  of,  151 
tinning  of,  327 
plates,  to  coat,  with  a  very  thin 

but  hard  layer  of  copper,  236 
precipitation  of  gold  by,  317 
properties  of,  333,  334 
red  brown  color  on,  414 
reduction  of  chloride  of  silver  by, 

286 

removal  of  oxide  from,  158 
scratch  brushes  for,  146 
sheet,  black   streaks  and   stains 

on,  in  nickeling,  208 
brassing  of,  206 
coppering  of,  206,  207 
current-density    for     nickel- 
ing, 207 
freeing  of,  from  grease,  204, 

205    • 
grinding  or  polishing  of,  200, 

201,  202 

nickel  bath  for,  178 
nickeled,  polishing  of,  208, 

209 

nickeling  of,  199-209 
phenomena  in  nickeling,  205, 

206 

polishing  of,  136 
prevention  of  the  nickel  de- 
posit peeling  off,  206 
vats  for  nickeling,  207 
sulphate,  442 
-tin  alloy,  production  of,  337 

-nickel  alloy,  production  of, 

337 

yellow  brown  shades  on,  414 
Zincking,  execution  of,  336,  337 

iron  by  contact,  337 
Zone,  neutral,  10 

Zosimus,  reduction  of  copper  from  its 
solution  by  iron  described  by,  1 


The  Hanson  &  Van  Winkle  Co.,  Newark,  N.  J.,  U.  S.  A. 

ELECTRO=PLATINQ  OUTFITS 

FOR 

Gold,  Silver,  Nickel,  Copper,  Etc. 


Just  a  Word  about  Dynamos. 

Did  you  know  that  all  the  early  experi- 
ments and  improvements  in  Dynamos  were 
made  with  a  view  of  perfecting  an  electrical 
machine  for  plating,  and  that  this  success 
was  the  forerunner  of  all  the  magnificent 
Dynamo  machines  for  other  purposes  in 
such  general  use  to-day? 

In    1876  we   began    manufacturing   the 

"  Weston"  Dynamo 
for  electro-plating. 
This  was  the  first 
machine  in  the  mar- 
ket. It  met  with 
pronounced  success, 
and  to  it  can  be 
traced  the  sudden 
development  of  electro-plating  and  electro- 
typing.  Many  of  these  machines  are  still 
in  use. 


The  Hanson  &  Van  Winkle  Co.,  Newark,  N.  J.,  U.  S.  A. 


In  1885  we 
brought  out  the 
"Little  Wonder" 
Dynamo.  It  be- 
came very  popular. 
Over  one  thousand 

were  sold. 
In  1886  we  be- 
gan manufacturing 
the     "Wonder' 
Dynamo.      It  em- 
bodied  many  new 
improvements,  and 
we    thought    then 
that  we  had  reached  perfection. 

In  1891  electrical  science  had  devel- 
oped so  many  en- 
tirely new  features, 
that  in  order  to 


maintain  our  emi- 
nent position  as 
leaders  in  the  pro- 
duction of  plating 

machines,  we  brought  out  our  H.  &  V.  W. 

Dynamo.      It    embodied    every    late    idea, 

and  has  had  a  remarkable  sale. 

(On  the  following  page  we  show  our  new  IRON  CLAD  Dynamo.    This 
also  marks  a  new  era  in  plating  dynamos.) 

2 


The  Hanson  &  Van  Winkle  Co.,  Newark,  N.  J.,  U.  S.  A. 


If  You  are  Interested 

in  Electro-plating,  Electro  typing,  Electro-refining  of  Metals  or 
other.  Electro-chemical  operations,  you  will  naturally  feel  in- 
terested in  anything  that  tends  to  bring  these  industries  to  the 
highest  stage  of  development. 

In  Introducing 

this  new  dynamo  to  your  notice,  we  feel  that  we  are  urging 
the  claims  of  a  machine  which  will  materially  aid  you  in 
reaching  that  point. 

Many 

who  have  only  used  the  old  style  machines  have  no  idea  of  the 
improvements  that  have  recently  been  made  in  this  class  of  dy- 
namos; improvements  that  save  time,  money,  labor  and  trouble. 

There  are  Several 

dynamos  which  are  marked  improvements  on  the  old  style  of 
machines,  but  the  new  IRON  CLAD,  while  embracing  all  the 
good  points  found  in  other  modern  machines,  has  several  im- 
provements distinctively  its  own,  and  is  the  result  of  years  of 
experimenting;  there  are  no  unusual  number  of  brushes  as  in 
some  other  Dynamos,  in  some  requiring  24  to  36  brushes  to 
wear  the  Commutator  and  the  patience  of  the  plater. 

3 


The  Hanson  &  Van  "Winkle  Co.,  Newark,  N.  J.,  U.  S.  A. 


CAST 
ANODES 


OF   ALL 


METALS 

ANY 

SIZE. 


Nickel: 

We  are  first  hands  in  nickel  and 
other  metals,  and  the  largest 
manufacturers  of  the  various 
Metallic  Salts,  of  Nickel,  Silver, 
Copper  and  Gold,  and  of 
Cyanide  of  Potassium. 

Plating  Solutions: 

We  furnish  Concentrated  Plat- 
ing] Solutions  of  Silver,  Gold, 
Copper,  Nickel,  Brass,  etc. 

Batteries 

of  all  kinds.  Our  No.  1  H.  & 
V.  W.  Battery  has  had  a  larger 
sale  than  any  other  for  Electro- 
Plating  and  experimental  work. 

Anodes : 

Our  Cast  Nickel  Anodes  are 
standard  for  whitest  results. 
Anodes  of  Nickel,  Silver, 
Gold,  Electro-deposited  Cop- 
per, Brass,  etc.  Nickel  cast- 
ings. 

Tanks:  i 

Porcelain-lined,  Iron,  Wood, 
Slate,  etc. ,  for  all  purposes. 

Lacquers : 

Patent  Celluloid  Lacquers  for 
metal,  paper,  etc.  Gold  and 
colored  Lacquers. 

Chemical  Solution : 

For  removing  sand,  scale,  etc. , 
from  castings,  etc. 


The  Hanson  &  Van  Winkle  Co.,  Newark,  N.  J.,  U.  S.  A. 

No.  4  Polishing  and  Buffing  Lathe. 


SPINDLE  50  INCHES  LONG,  If  INCH  DIAMETER  IN  BOXES. 

This  machine  is  designed  for  heavy  work.  It  is  fitted  with  extra  long 
boxes,  giving  the  spindle  sufficient  bearing  to  insure  stiffness.  Without 
sacrificing  strength,  we  have  so  reduced  the  width  of  head  that  the  ma- 
chine will  be  found  especially  desirable  by  manufacturers  of  large,  irreg- 
ular pieces,  and  will  commend  itself  to  any  one  having  bicycle,  stove, 
chandelier  or  car  trimmings  to  do,  as  with  this  lathe  there  is  no  inter- 
ference when  working  on  large  pieces.  With  this  machine  you  can  use 
a  large  wheel  without  the  slightest  jar  or  spring. 

We  show  above  a  sample  of  one  of  our  most  salable  Polishing 
Lathes. 

5 


The  Hanson  &  Van  Winkle  Co.,  Newark,  N.  J.,  U.  S.  A. 


We  manufacture  a  complete  line  of; 


GRINDING,-  ; 

Polishing  and  Buffing  Machines, 


and  all  the 


Various  Wheels  and  Buffs  and  Grinding 
and  Polishing  Material. 


FELT  VIENNA  LIME 

COMPRESS  CARBORUNDUM 

EMERY  WOOD 

CROCUS  SHEEPSKIN 

WALRUS  ROUGE 


PAPER 


PUMICE 


6 


The  Hanson  &  Van  "Winkle  Co.,  Newark,  N.  J.,  U.  S.  A. 


POLISHING  SUPPLIES. 


TRIPOLI  COMPOSITION. 

•Tripoli  Composition  is  especially  adapted  for  cutting  down  and 
polishing  Brass,  Bronze,  Brittannia,  and  other  metals  preparatory 
to  plating. 

Standard  Tripoli  Composition,  O.  S.  for  cutting  and  polishing,       .       per  Ib. 

"  "  "  M,  very  greasy        ....  " 

"  "  "  No.  6,  hard  and  fast  cutting   .         .  " 

"  "  "  H,  very  fast  cutting         ...  " 

No.  9,  similar  to  O.  S. ,  slightly  sharper,     ' ' 

CROCUS  COMPOSITION. 

Crocus  Composition  is  largely  used  by  stove  manufacturers  and 
others  desiring  to  produce  smooth  finished  surface  on  cast  iron  and 
steel. 

A,  greasy,  fast  cutting        .         .         .         .  .....  .       per  Ib. 

F.  F.,  dry  and  fast  cutting          .         .         .  .  .  .         . 

S,  dry  and  fast  cutting        .         .         .         .  .  .  .         .  « 

O.  S.,  very  finest  grade  of  this  material      .  .  „  »    .    «  .           " 

Emery  Cake *~    "\  .           " 

Emery  Paste      .       V       ,        •        «        .  .  .  .,       ..  \           " 

English  Crocus,  powdered,  in  kegs  and  casks  .  .  -    .         .  .           " 

7 


The  Hanson  &  Van  Winkle  Co.,  Newark,  N.  J.,  U.  S.  A. 


POLISHING  SETT. 


No.  200 
Complete  Box  of  Polishing  Tools  and  Powders  for  small  work       .         .         $3.00 

When  ordered  with  No.  22  or  24  Lathe,  $2.00,  with  samples  of  Lacquer. 

8 


The  Hanson  &  Van  Winkle  Co.,  Newark,  N.  J.,  U.  S.  A. 

XXX  BUFFING  COMPOUND. 

For  polishing  and  coloring  all  metals  where  the  higher  color  is 
required,  with  the  greatest  economy  of  time,  and  especially  for 
work  that  is  engraved  or  ornamented  where  rouge  is  objectionable. 

Put  up  in  cakes  similar  to  Tripoli       : '•*,..         .         .         per  Ib. 

VIENNA  LlflE. 

We  are  the  largest  importers  of  this  article,  and  furnish  it  both 
in  lump  and  powder,  and  send  full  instructions  for  getting  best 
results.  There  is  an  increasing  demand  for  this  article  for  nickel 
and  other  work,  and  we  are  paying  special  attention  to  the  quality. 


Our  1(>0  page  Catalogue  mailed  on  application  to  any  ad- 
dress in  the  w«>rld. 


THE  HANSON  8  VfiN  WINKLE  CO., 

MANUFACTORY  AND   OFFICES: 

219  &  221  flarket  Street, 

Newark,  N.  J.,  U.  S.  A. 


NEW  YORK  OFFICE :  WESTERN  BRANCH  : 

136  Liberty  Street.  35  &  37  S.  Canal  St.,  Chicago,  111. 

13  St.  Paul  Square,  Birmingham,  England. 

9 


OF 


practical  and  Scientific 

PUBLISHED  BY 

HENRY  CAREY  BAIRD  &  Co, 


INDUSTRIAL  PUBLISHERS,  BOOKSELLERS  AND  IMPORTERS. 

810  Walnut  Street,  Philadelphia. 


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AMATEUR  MECHANICS'  WORKSHOP: 

A  treatise  containing  plain  and  concise  directions  for  the  manipula- 
tion of  Wood  and  Metals,  including  Casting,  Forging,  Brazing, 
Soldering  and  Carpentry.  By  the  author  of  the  "  Lathe  and  Its 
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ANDRES.— A  Practical  Treatise  on  th«  Fabrication  of  Volatile 
and  Fat  Varnishes,  Lacquers,  Yiccatives  and  Sealing 
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From  the  German  of  ERWIN  ANDRES,  Manufacturer  of  Varnishes 
and  Lacquers.  With  additions  on  the  Manufacture  and  Application 
of  Varnishes,  Stains  for  Wood,  Horn,  Ivory,  Bone  and  Leather. 
From  the  German  of  DR.  EMIL  WINCKLER  and  Louis  E.  ANDES. 
The  whole  translated  and  edited  by  WILLIAM  T.  BRANNT.  With  n 
illustrations.  I2mo.  ....... 

ARLOT. — A  Complete  Guide  for  Coach  Painters : 

Translated  from  the  French  of  M.  ARLOT,  Coach  Painter,  for 
eleven  years  Foreman  of  Painting  to  M.  Eherler,  Coach  Maker, 
Paris.  By  A.  A.  FESQUET,  Chemist  and  Engineer.  To  which  is 
added  an  Appendix,  containing  Information  respecting  the  Materials 
and  the  Practice  of  Coach  and  Car  Painting  and  Varnishing  in  the 
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ARMENGAUD,  AMOROUX,  AND  JOHNSON.— The  Practi- 
cal Draughtsman's  Book  of  Industrial  Design,  and  Ma^ 
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Forming  a  Complete  Course  of  Mechanical  Engineering  and  Archi 
tectural  Drawing.  From  the  French  of  M  Armengaud  the  elder, 
Prof,  of  Design  in  the  Conservatoire  of  Arts  and  Industry,  Paris,  and 
MM.  Armengaud  the  younger,  and  Amoroux,  Civil  Engineers.  Re- 
written and  arranged  with  additional  matter  and  plates,  selections  from 
and  examples  of  the  most  useful  and  generally  employed  mechanism 
of  the  day.  By  WILLIAM  JOHNSON,  Assoc.  Inst.  C.  E.  Illustrated 
by  fifty  folio  steel  plates,  and  fifty  wood-cuts.  A  new  edition,  4to  , 

cloth $6.00 

ARMSTRONG. — The  Construction  and  Management  of  Steam 

Boilers  : 

By  R.  ARMSTRONG,  C.  E.  With  an  Appendix  by  ROBERT  MALLET, 
C.  E.,  F.  R.  S.  Seventh  Edition.  Illustrated.  I  vol.  I2mo.  75 

ARROWSMITH.— Paper-Hanger's  Companion : 

A  Treatise  in  which  the  Practical  Operations  of  the  Trade  are 
Systematically  laid  down :  with  Copious  Directions  Preparatory  to 
Papering;  Preventives  against  the  Effect  of  Damp  on  Walls;  the 
various  Cements  and  Pastes  Adapted  to  the  Several  Purposes  ol 
the  Trade ;  Observations  and  Directions  for  the  Panelling  and 
Ornamenting  of  Rooms,  etc.  By  JAMES  ARROWSMITH.  I2mo., 
cloth  ..........  $1.00 

A.SHTON. — The  Theory  and  Practice  of  the  Art  of  Designing 

Fancy  Cotton  and  Woollen  Cloths  from  Sample  : 
Giving  full  instructions  for  reducing  drafts,  as  well  as  the  methods  of 
spooling  and  making  out  harness  for  cross  drafts  and  finding  any  re- 
quired reed;  with  calculations  and  tables  of  yarn.  By  FREDERIC  T. 
ASHTON,  Designer,  West  Pittsfield,  Mass.  With  fifty-two  illustrations. 
One  vol.  folio  #5-°° 

ASKINSON. — Perfumes  and  their  Preparation  : 

A  Comprehensive  Treatise  on  Perfumery,  containing  Complete 
Directions  for  Making  Handkerchief  Perfumes,  Smelling-Salts, 
Sachets,  Fumigating  Pastils ;  Preparations  for  the  Care  of  the  Skin, 
the  Mouth,  the  Hair;  Cosmetics,  Hair  Dyes,  and  other  Toilet 
Articles.  By  G.  W.  ASKINSON.  Translated  from  the  German  by  IsiDOR 
FURST.  Revised  by  CHARLES  RICE.  32  Illustrations.  8vo.  $3.00 

3AIRD.— Miscellaneous     Papers     on     Economic     Questions. 
By  Henry  Carey  Baird.     {In  preparation.} 

BAIRD.— The  American  Cotton  Spinner,  anc   Manager's  and 

Carder's  Guide: 

A  Practical  Treatise  on  Cotton  Spinning ;  giving  the  Dimensions  and 
Speed  of  Machinery,  Draught  and  Twist  Calculations,  etc. ;  with 
notices  of  recent  Improvements :  together  with  Rules  and  Examples 
rbr  making  changes  in  the  sizes  and  numbers  of  Roving  and  Yarn. 
Compiled  from  the  papers  of  the  late  ROBERT  H.  BAIRD.  i2mo. 


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BAIRD. — Standard  Wages  Computing  Tables  : 

An  Improvement  in  all  former  Methods  of  Computation,  so  arranged 
that  wages  for  days,  hours,  or  fractions  of  hours,  at  a  specified  rate 
per  day  or  hour,  may  be  ascertained  at  a  glance.  By  T.  SPANGLER 
BAIRD.  Oblong  folio  .......  $5.00 

3AKER. — Long-Span  Railway  Bridges: 

Comprising  Investigations  of  the  Comparative  Theoretical  and 
Practical  Advantages  of  the  various  Adopted  or  Proposed  Type 
Systems  of  Construction;  with  numerous  Formulae  and  Tables.  By 
B.  BAKER.  i2mo. $1.00 

BAKER.— The  Mathematical  Theory  of  the  Steam-Engine  : 
With   Rules  at  length,  and   Examples  worked  out   for  the  use  of 
Practical   Men.     By  T.   BAKER,   C.   E.,  with   numerous  Diagrams. 
Sixth  Edition,  Revised  by  Prof.  J.  R.  YOUNG.     I2mo.          .  75 

BARLOW. — The    History    and    Principles    of    Weaving,   by 

Hand  and  by  Power: 

Reprinted,  with  Considerable  Additions,  from  "  Engineering,"  with 
a  chapter  on  Lace-making  Machinery,  reprinted  from  the  Journal  of 
the  "Society  of  Arts."  By  ALFRED  BARLOW.  With  several  hundred 
illustrations.  8vo.,  443  pages  .....  $10.00 

BARR. — A  Practical  Treatise  on  the  Combustion  of  Coal: 
Including  descriptions  of  various  mechanical  devices  for  the  Eco- 
nomic Generation  of  Heat  by  the  Combustion  of  Fuel,  whether  solid, 
liquid  or  gaseous.     8vo.     .......         $2.50 

BARR. — A  Practical  Treatise  on  High  Pressure  Steam  Boilers: 
Including  Results  of  Recent  Experimental  Tests  of  Boiler  Materials, 
together  with  a  Description  of  Approved  Safety  Apparatus,  Steam 
Pumps,  Injectors  and  Economizers  in  actual  use.  By  WM.  M.  BARR. 
204  Illustrations.  8vo.  .  ....".  $3.00 

BAUERMAN.— A  Treatise  on  the  Metallurgy  of  Iron : 

Containing  Outlines  of  the  History  of  Iron  Manufacture,  Methods  of 
Assay,  and  Analysis  of  Iron  Ores,  Processes  of  Manufacture  of  Iron 
and  Steel,  etc.,  etc.     By  H.  BAUERMAN,  F.  G.  S.,  Associate  of  the 
Royal  School  of   Mines.      Fifth    Edition,    Revised    and    Enlarged. 
Illustrated  with  numerous  Wood  Engravings  from  Drawings  by  J.  B. 
JORDAN.     i2mo.       ........        $2.oc 

BRAN  NT.— The  Metallic  Alloys  :  A  Practical  Guide 

For  the  Manufacture  of  all  kinds  of  Alloys,  Amalgams,  and  Solders, 
used  by  Metal- Workers;  together  with  their  Chemical  and  Physical 
Properties  and  their  Application  in  the  Arts  and  the  Industries;  with 
an  Appendix  on  the  Coloring  of  Alloys  and  the  Recovery  of  Waste 
Metals.  By  WILLIAM  T.  BRANNT.  34  Engravings.  A  New,  Re- 
vised, and  Enlarged  Edition.  554  pages.  8vo.  .  .  $4.50 

BEANS.— A   Treatise   on   Railway  Curves    and   Location  of 

Railroads : 
By  E.  \V.  BEANS,  C.  E.     Illustrated.     I2mo.     Tucks        .         $1.50 

BECKETT. — A  Rudimentary  Treatise  on  Clocks,  and  Watches 

and  Bells  : 

By  Sir  EDMUND  BECKETT,  Bart.,  LL.  D.,  Q.  C.  F.  R.  A.  S.  With 
numerous  illustrations.  Seventh  Edition,  Revised  and  Enlarged. 
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BELL. — Carpentry  Made  Easy: 

Or,  The  Science  and  Art  of  Framing  on  a  New  and  Improved 
System.  With  Specific  Instructions  for  Building  Balloon  Frames,  Barn 
Frames,  Mill  Frames,  Warehouses,  Church  Spires,  etc.  Comprising 
also  a  System  of  Bridge  Building,  with  Bills,  Estimates  of  Cost,  and 
valuable  Tables.  Illustrated  by  forty-four  plates,  comprising  Dearly 
200  figures.  By  WILLIAM  E.  BELL,  Architect  and  Practical  Builder. 
8vo.  ..........  $5.00 

BEMROSE. — Fret-Cutting  and  Perforated  Carving: 

With  fifty-three  practical  illustrations.  By  W.  BEMROSE,  JR.  i  vol. 
quarto  ..........  $2.50 

BEMROSE. — Manual  of  Buhl-work  and  Marquetry: 

With  Practical  Instructions  for  Learners,  and  ninety  colored  designs. 
By  W.  BEMROSE,  JR.  I  vol.  quarto  ....  $3.00 

BEMROSE. — Manual  of  Wood  Carving: 

With  Practical  Illustrations  for  Learners  of  the  Art,  ~.nd  Original  and 
Selected  Designs.  By  WILLIAM  BEMROSE,  JR.  With  an  Intro- 
duction by  LLEWELLYN  JEWITT,  F.  S.  A.,  etc.  With  128  illustra- 
tions, 410. -.  #2.50 

BILLINGS.— Tobacco : 

Its  History,  Variety,  Culture,  Manufacture,  Commerce,  and  Various 
Modes  of  Use.  By  E.  R.  BILLINGS.  Illustrated  by  nearly  200 
engravings.  8vo.  .  .  .  .  .  .  .  #3.00 

BIRD. — The  American  Practical  Dyers'  Companion : 
Comprising  a  Description  of  the  Principal  Dye-Stuffs  and  Chemicals 
used  in  Dyeing,  their  Natures  and  Uses;  Mordants,  and  How  Made; 
with  the  best  American,  English,  French  and  German  processes  for 
Bleaching  and  Dyeing  Silk,  Wool,  Cotton,  Linen,  Flannel,  Felt, 
Dress  Goods,  Mixed  and  Hosiery  Yarns,  Feathers,  Grass,  Felt,  Fur, 
Wool,  and  Straw  Hats,  Jute  Yarn,  Vegetable  Ivory,  Mats,  Skins, 
Furs,  Leather,  etc.,  etc.  By  Wood,  Aniline,  and  other  Processes, 
together  with  Remarks  on  Finishing  Agents,  and  Instructions  in  the 
Finishing  of  Fabrics,  Substitutes  for  Indigo,  Water-Proofing  of 
Materials,  Tests  and  Purification  of  Water,  Manufacture  of  Aniline 
and  other  New  Dye  Wares,  Harmonizing  Colors,  etc.,  etc. ;  embrac- 
ing in  all  over  800  Receipts  for  Colors  and  Shades,  accompanied  by 
170  Dyed  Samples  of  Raw  Materials  and  Fabrics.  By  F.  J.  BIRD, 
Practical  Dyer,  Author  of  "  The  Dyers'  Hand-Book."  8vo.  $10.00 

BLINN. — A  Practical  Workshop  Companion  for  Tin,  Sheet- 

Iron,  and  Copper-plate  Workers  : 

Containing  Rules  for  describing  various  kinds  of  Patterns  used  by 
Tin,  Sheet-Iron  and  Copperplate  Workers;  Practical  Geometry; 
Mensuration  of  Surfaces  and  Solids ;  Tables  of  the  Weights  of 
Metals,  Lead-pipe,  etc.;  Tables  of  Areas  and  Circumference* 
of  Circles;  Japan,  Varnishes,  Lackers,  Cements,  Compositions,  etc., 
etc.  By  LEROY  J.  BLINN,  Master  Mechanic.  With  One  Hundred 
and  Seventy  Illustrations.  I2tno.  .  .  »  .  .  .  $2.50 


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BOOTH.— Marble  Worker's  Manual: 

Containing  Practical  Information  respecting  Marbles  in  general,  theii 
Cutting,  Working  and  Polishing ;  Veneering  of  Marble  ;  Mosaics ; 
Composition  and  Use  of  Artificial  Marble,  Stuccos,  Cements,  Receipts, 
Secrets,  etc.,  etc.  Translated  from  the  French  by  M.  L.  BOOTH. 
With  an  Appendix  concerning  American  Marbles.  I2mo.,  cloth  $1.50 

BOOTH    and    MORFIT. — The    Encyclopaedia   of    Chemistry, 

Practical  and  Theoretical : 

•Embracing  its  application  to  the  Arts,  Metallurgy,  Mineralogy, 
Geology,  Medicine  and  Pharmacy.  By  JAMES  C.  BOOTH,  Melter 
and  Refiner  in  the  United  States  Mint,  Professor  of  Applied  Chem- 
istry in  the  Franklin  Institute,  etc.,  assisted  by  CAMPBELL  MORFIT, 
author  of  "  Chemical  Manipulations,"  etc.  Seventh  Edition.  Com- 
plete in  one  volume,  royal  8vo.,  978  pages,  with  numerous  wood-cuts 
and  other  illustrations  .  .  .  .  .  .  »  $3-5° 

BRAM WELL.— The  Wool  Carder's  Vade-Mecum, 

A  Complete  Manual  of  the  Art  of  Carding  Textile  Fabrics.  By  W. 
C.  BRAMWELL.  Third  Edition,  revised  and  enlarged.  Illustrated. 
Pp.  400.  I2mo $2.50 

BRANNT.— A   Practical  Treatise  on  Animal  and  Vegetable 

Fats  and  Oils  : 

Comprising  both  Fixed  and  Volatile  Oils,  their  Physical  and  Chem- 
ical Properties  and  Uses,  the  Manner  of  Extracting  and  Refining 
them,  and  Practical  Rules  for  Testing  them ;  as  well  as  the  Manufac- 
ture of  Artificial  Butter  and  Lubricants,  etc.,  with  lists  of  American 
Patents  relating  to  the  Extraction,  Rendering,  Refining,  Decomposing, 
and  Bleaching  of  Fats  and  Oils.  By  WILLIAM  T.  BRANNT,  Editor 
of  the  "  Techno-Chemical  Receipt  Book."  Second  Edition,  Revised 
and  in  a  great  pi>rt  Rewritten.  Illustrated  by  302  Engravings.  In 
Two  Volumes.  1304  pp.  8vo.  .....  $10.00 

BRANNT. — A  Practical  Treatise  on  the  Manufacture  of  Soap 

and  Candles : 

Based  upon  the  most  Recent  Experiences  in  the  Practice  and  Science ; 
comprising  the  Chemistry,  Raw  Materials,  Machine-v.  and  Utensils 
and  Various  Processes  of  Manufacture,  including  a  great  variety  of 
formulas.  Edited  chiefly  from  the  German  of  Dr.  C.  Deite,  A. 
Engelhardt,  Dr.  C.  Schaedler  and  others ;  with  additions  and  list? 
of  American  Patents  relating  to  these  subjects.  By  WM.  T.  BRANNT. 
Illustrated  by  163  engravings.  677  pages.  8vo.  .  .  #7.50 

BRANNT. — A  Practical  Treatise  on  the  Raw  Materials  and  the 
Distillation  and  Rectification  of  Alcohol,  and  the  Prepara- 
tion of  Alcoholic  Liquors,  Liqueurs,  Cordials,  Bitters,  etc.: 
Edited  chiefly  from  the  German  of  Dr.  K.  Stammer,  I)r.  F.  Eisner, 
and  E.  Schubert.     By  WM.  T.  BRANNT.     Illustrated  by  thirty-one 
engravings.     I2mo.  .......         $3-5° 


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BRANNT—  WAHL.—  The  Techno-Chemical  Receipt  Book: 

Containing  several  thousand  Receipts  covering  the  latest,  most  ;ra 
portant,  and  most  useful  discoveries  in  Chemical  Technology,  and 
their  Practical  Application  in  the  Arts  and  the  Industries.  Edited 
chiefly  from  the  German  of  Drs.  Winckler,  Eisner,  Heintze,  Mier- 
zinski,  Jacobsen,  Koller,  and  Heinzerling,  with  additions  by  WM.  1» 
BRANNT  and  WM.  H.  WAHL,  PH.  D.  Illustrated  by  78  engravings. 
I2mo.  495  pages  ...  ...  .  552  oO 

1  ROWN.  —  Five  Hundred  and  Seven  Mechanical  Movements: 
Embracing  all  those  which  are  most  important  in  Dynamics,  Hy- 
draulics, Hydrostatics,  Pneumatics,  Steam-Engines,  Mill  and  other 
Gearing,  Presses,  Horology  and  Miscellaneous  Machinery;  and  in- 
cluding many  movements  never  before  published,  and  several  of 
which  have  only  recently  come  into  use.  By  HENRY  T.  BROWN 
I2mo  ...........  $i.oc 

BUCKM  ASTER.—  The  Elements  of  Mechanical  Physics  : 
By  J.   C.   BUCKMASTER.       Illustrated    with    numerous    engravings. 
I2mo  ...........         $1.00 

BULLOCK.  —  The  American  Cottage  Builder  : 

A  Series  of  Designs,  Plans  and  Specifications,  from  $200  to  $20,000, 
for  Homes  for  the  People  ;  together  with  Warming,  Ventilation, 
Drainage,  Painting  and  Landscape  Gardening.  By  JOHN  BULLOCK, 
Architect  and  Editor  of  "  The  Rudiments  of  Architecture  and 
Building."  etc.,  elc.  Illustrated  by  75  engravings.  8vo.  $2-5° 

BULLOCK.  —  The  Rudiments  of  Architecture  and  Building: 
For  the  use  of  Architects,   Builders,   Draughtsmen,   Machinists,  En- 
gineers and  Mechanics.     Edited  by  JOHN  BULLOCK,  author  of  "The 
American  Cottage  Builder."   Illustrated  by  250  Engravings.  8vo.  $2.50 

BURGH.—  Practical    Rules    for    the   Proportions   of     Modern 

Engines  and  Boilers  for  Land  and  Marine  Purposes. 
By  N.  P.  BURGH,  Engineer.     I2mo.  ....         $1.50 

BYLES.  —  Sophisms    of     Free    Trade    and    Popular    Political 

Economy  Examined. 

13y  a  BARRISTER  (SIR  JOHN  BARNARD  BYLES,  Judge  of  Common 
Pleas).  From  the  Ninth  English  Edition,  as  published  by  ihc 
Manchester  Reciprocity  Association.  I2mo.  .  .  .  $1.25 

BOWMAN.—  The  Structure  of  the  Wool  Fibre  in  its  Relation 

to  the  Use  of  Wool  for  Technical  Purposes  : 
Being  the  substance,  with  additions,  of  Five  Lectures,  deliverea  <it 
v.he  request  of  the  Council,  to  the  members  of  the  Bradford  Technical 
College,  and  the  Society  of  Dyers  and  Colorists.  By  F.  H.  BOW- 
MAN, D.  Sc.,  F.  R.  S.  E.,  F.  L.  S.  Illustrated  by  32  engravings. 
8vo.  ..........  $6.50 

BYRNE.  —  Hand-Book  for  the  Artisan,  Mechanic,  and 


Comprising  the  Grinding  and  Shnrpening  of  Cutting  Tools,  Abra-.ve 
Processes,  Lapidary  Work,  Gem  and  Glass  Engraving,  Varnishing 
and  Lackering,  Apparatus,  Materials  and  Processes  for  Grinding  and 


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Polishing,  etc.  By  OLIVER  BYRNE.  Illustrated  by  185  wood  en- 
gravings. 8vo.  ........  $5.00 

BYRNE. — Pocket-Book  for  Railroad  and  Civil  Engineers : 
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Curves,  Switches,  Frog  Angles  and  Crossings ;  the  Staking  out  of 
work ;  Levelling ;  the  Calculation  of  Cuttings  ;  Embankments ;  Earth- 
work, etc.  By  OLIVER  BYRNE.  i8mo.,  full  bound,  pocket-book 
form $1.50 

BYRNE.— Trie  Practical  Metal-Worker's  Assistant: 
Comprising  Metallurgic  Chemistry;  the  Arts  of  Working  all  Metals 
and  Alloys:  Forging  of  Iron  and  Steel;  Hardening  and  Tempering; 
Melting  and  Mixing;  Casting  and  Founding;  Works  in  Sheet  Metal; 
the  Processes  Dependent  on  the  Ductility  of  the  Metals;  Soldering; 
and  the  most  Improved  Processes  and  Tools  employed  by  Metal- 
workers. With  the  Application  of  the  Art  of  Electro-Metallurgy  to 
Manufacturing  Processes;  collected  from  Original  Sources,  and  from 
the  works  of  Holtzapffel,  Bergeron,  Leupold,  Plumier,  Napier, 
Scoffern,  Clay,  Fairbairn  and  others.  'By  OLIVER  BYRNE.  A  new, 
revised  and  improved  edition,  to  which  is  added  an  Appendix,  con- 
taining The  Manufacture  of  Russian  Sheet- Iron.  By  JOHN  PERCY, 
M.  D.,  F.  R.  S.  The  Manufacture  of  Malleable  Iron  Castings,  and 
Improvements  in  Bessemer  Steel.  By  A.  A.  FESQUET,  Chemist  and 
Engineer.  With  over  Six  Hundred  Engravings,  Illustrating  every 
Branch  of  the  Subject.  8vo $5-OO 

BYRNE.— The  Practical  Model  Calculator: 

For  the  Engineer,  Mechanic,  Manufacturer  of  Engine  Work,  Nava* 
Architect,  Miner  and  Millwright.  By  OLIVER  BYRNE.  8vo.r  nearly 
600  pa^es $3  oo 

CAHINET  MAKER'S  ALBUM  OF  FURNITURE °. 

Comprising  a  Collection  of  Designs  for  various  Styles  of  Furniture. 
Illustrated  by  Forty-eight  Large  and  Beautifully  Engraved  Plates. 
Oblong,  8vo.  ........  $l.$o 

CALLINGHAM. — Sign  Writing  and  Glass  Embossing: 

A  Complete  Practical  Illustrated  Manual  of  the  Art.  By  JAMES 
CALLINGHAM.  121110 $1.50 

CAMPIN. — A  Practical  Treatise  on  Mechanical  Engineering: 
Comprising  Metallurgy,  Moulding,  Casting,  Forging,  Tools,  Work- 
shop  Machinery,  Mechanical  Manipulation,  Manufacture  of  Steam- 
Engines,  etc.  With  an  Appendix  on  the  Analysis  of  Iron  and  Iron 
Ores.  By  FPANCIS  CAMPIN,  C.  E.  To  which  are  added,  Observations 
on  the  Construction  of  Steam  Boilers,  and  Remarks  upon  Furnaces 
used  for  Smoke  Prevention ;  with  a  Chapter  on  Explosions.  By  R. 
ARMSTRONG,  C.  E.,  and  JOHN  BOURNE.  Rules  for  Calculating  th« 
Change  Wheels  for  Screws  on  a  Turning  Lathe,  and  for  a  Wheel- 
cutting  Machine.  By  J.  LA  NICCA.  Management  of  Steel,  Includ- 
ing P'orging,  Hardening,  Tempering,  Annealing,  Shrinking  and 
Expansion  ;  and  the  Case-hardening  of  Iron.  By  G.  EDF.  8vo. 
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CAREY.— A  Memoir  of  Henry  C.  Carey. 

By  DR.  WM.  ELDER,    With  a  portrait.     8vo.,  cloth         .         .        75 

CAREY.— The  Works  of  Henry  C.  Carey : 

Harmony  of  Interests  :    Agricultural,  Manufacturing  and  Commer. 
cial.     8vo.  .....  .  $1.25 

Manual  of  Social  Science.  Condensed  from  Carey's  "  Principle* 
of  Social  Science."  By  KATE  McKEAN.  I  vol.  I2mo.  .  $2.00 
Miscellaneous  Works.  With  a  Portrait.  2  vols.  8vo.  $10.00 

Past,  Present  and  Future.     8vo $2.50 

Principles  of  Social  Science.  3  volumes,  8vo.  .  .  $7.50 
The  Slave-Trade,  Domestic  and  Foreign;  Why  it  Exists,  and 
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The  Unity  of  Law :  As  Exhibited  in  the  Relations  of  Physical, 
Social,  Mental  and  Moral  Science  (1872).  8vo.  .  .  $2.50 

CLARK. — Tramways,  their  Construction  and  Working : 

Embracing  a  Comprehensive  History  of  the  System.  With  an  ex 
haustive  analysis  of  the  various  modes  of  traction,  including  horse- 
power, steam,  heated  -water  a*nd  compressed  air;  a  description  of  the 
varieties  of  Rolling  stock,  and  ample  details  of  cost  and  working  ex- 
penses.  By  D.  KINNEAR  CLARK.  Illustrated  by  over  200  wood 
engravings,  and  thirteen  folding  plates.  I  vol.  8vo.  .  $7.50 

COLBURN. — The  Locomotive  Engine  : 

Including  a  Description  of  its  Structure,  Rules  for  Estimating  its 
Capabilities,  and  Practical  Observations  on  its  Construction  and  Man 
agement.  By  ZERAH  COLBURN.  Illustrated.  I2mo.  .  #1.00 

COLLENS. — The  Eden  of  Labor ;  or,  the  Christian  Utopia. 
By  T.  WHARTON  COLLENS,  author  of  "  Humanics,"    "  The  Historj 
of  Charity,"  etc.     I2mo.     Paper  cover,  $1.00;   Cloth          .         $1.25 

COOLEY. — A  Complete  Practical  Treatise  on  Perfutnery : 
Being  a  Hand-book  of  Perfumes,  Cosmetics  and  other  Toilet  Articles 
With   a  Comprehensive    Collection  of  Formulae.     By   ARNOLD  J 
COOLEY.    i2mo.        . $1.50. 

COOPER. — A  Treatise  on  the  use  of  Belting  for  the  Trans 

mission  of  Power. 

With  numerous  illustrations  of  approved  and  actual  methods  of  ar 
ranging  Main  Driving  and  Quarter  Twist  Belts,  and  of  Belt  Fasten 
ings.  Examples  and  Rules  in  great  number  for  exhibiting  and  cal 
culating  the  size  and  driving  power  of  Belts.  Plain,  Particular  and 
Practical  Directions  for  the  Treatment,  Care  and  Management  o7 
Belts.  Descriptions  of  many  varieties  of  Beltings,  together  witn 
chapters  on  the  Transmission  of  Power  by  Ropes;  by  Iron  and 
Wood  Frictional  Gearing;  on  the  Strength  of  Belting  Leather;  and 
on  the  Experimental  Investigations  of  Morin,  Briggs,  and  others.  Bj> 
JOHN  H.  COOPER,  M.  E.  8vo 

CRAIK. — The  Practical  American  Millwright  and  M^ler. 
By  DAVID  CRAIK,  Millwright.     Illustrated  by  numerous  wood  en 
gravings  and  two  folding  plates.     8vo $3.50 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.  9 

CROSS. — The  Cotton  Yarn  Spinner : 

Showing  how  the  Preparation  should  be  arranged  for  Different 
Counts  of  Yarns  by  a  System  more  uniform  than  has  hitherto  been 
practiced ;  by  having  a  Standard  Schedule  from  which  we  make  all' 
our  Changes.  By  RICHARD  CROSS.  122  pp.  I2mo.  .  75 

CRISTIANI. — A  Technical  Treatise  on  Soap  and  Candles: 

With  a  Glance  at  the  Industry  of  Fats  and  Oils.  By  R.  S.  CRIS- 
TIANI, Chemist.  Author  of  "  Perfumery  and  Kindred  Arts."  Illus- 
trated by  176  engravings.  581  pages,  8vo.  .  .  .  $15.00 

COAL  AND  METAL  MINERS'  POCKET  BOOK: 

Of  Principles,  Rules,  Formulae,  and  Tables,  Specially  Compiled 
and  Prepared  for  the  Convenient  Use  of  Mine  Officials,  Mining  En- 
gineers, and  Students  preparing  themselves  for  Certificates  of  Compe- 
tency as  Mine  Inspectors  or  Mine  Foremen.  Revised  and  Enlarged 
edition.  Illustrated,  565  pages,  small  I2mo.,  cloth.  ',  $2.00 

Pocket  book  form,  flexible  leather  with  flap  .         .  #2.75 

DAVIDSON. — A  Practical  Manual  of  House  Painting,  Grain- 
ing, Marbling,  and  Sign- Writing: 

Containing  full  information  on  the  processes  of  House  Painting  in 
Oil  and  Distemper,  the  Formation  of  Letters  and  Practice  of  Sign- 
Writing,  the  Principles  of  Decorative  Art,  a  Course  of  Elementary 
Drawing  for  House  Painters,  Writers,  etc.,  and  a  Collection  of  Useful 
Receipts.  W7ith  nine  colored  illustrations  of  Woods  and  Marbles, 
and  numerous  wood  engravings.  By  ELLIS  A.  DAVIDSON.  I2tno. 

#3°° 
DAVIES. — A  Treatise  on  Earthy  and  Other    Minerals   and 

Mining: 

By  D.  C.  DAVIES,  F.  G.  S.,  Mining  Engineer,  etc.  Illustrated  by 
76  Engravings.  I2mo. .  $S°° 

DAVIES. — A  Treatise  on  Metalliferous  Minerals  and  Mining: 
By  D.  C.  DAVIES,  F.  G.  S.,  Mining  Engineer,  Examiner  of  Mines, 
Quarries  and  Collieries.  Illustrated  by  148  engravings  of  Geological 
Formations,  Mining  Operations  and  Machinery,  drawn  from  the 
practice  of  all  parts  of  the  world.  Fifth  Edition,  thoroughly  Revised 
and  much  Enlarged  by  his  son,  E.  Henry  Davies.  I2mo.,  524 
pages  .  .  .  .  .  .  .  .  •  $$-oo 

DAVIES. — A  Treatise  on  Slate  and  Slate  Quarrying: 

Scientific,  Practical  and  Commercial.  By  D.  C.  DAVIES,  F.  G.  S., 
Mining  Engineer,  etc.  With  numerous  illustrations  and  folding 
plates.  I2mo. .  .  $2.00 

DAVIS.— A  Practical  Treatise  on  the  Manufacture  of  Brick, 

Tiles  and  Terra-Cotta : 

Including  Stiff  Clay,  Dry  Clay,  Hand  Made,  Pressed  or  Front,  and 
Roadway  Paving  Brick,  Enamelled  Brick,  with  Glazes  and  Colors, 
Fire  Brick  and  Blocks,  Silica  Brick,  Carbon  Brick,  Glass  Pots,  Re- 


10          HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 


torts,  Architectural  Terra-Cotta,  Sewer  Pipe,  Drain  Tile,  Glazed  and 
Unglazed  Roofing  Tile,  Art  Tile,  Mosaics,  and  Imitation  of  Intnrsia 
^  or  Inlaid  Surfaces.  Comprising  every  product  of  Clay  employed  in 
Architecture,  Engineering,  and  the  Blast  Furnace.  With  a  Detailed 
Description  of  the  Different  Clays  employed,  the  Most  Modern 
Machinery,  Tools,  and  Kilns  used,  and  the  Processes  for  Handling, 
Disintegrating,  Tempering,  and  Moulding  the  Clay  into  Shape,  Dry- 
ing, Setting,  and  Burning.  By  Charles  Thomas  Davis.  Third  Edi- 
tion, Revised  and  in  great  part  rewritten.  Illustrated  by  261 
engravings.  662  pages  .  .  .  .  .  .  .  $5  oo 

DAVIS. — A  Treatise  on  Steam-Boiler  Incrustation  and  Meth- 
ods for  Preventing  Corrosion  and  the  Formation  of  Scale: 
By  CHARLES  T.  DAVIS.     Illustrated  by  65  engravings.     8vo.    $2.00 

DAVIS. — The  Manufacture  of  Paper: 

Being  a  Description  of  the  various  Processes  for  the  Fabrication, 
Coloring  and  Finishing  of  every  kind  of  Paper,  Including  the  Dif- 
ferent Raw  Materials  and  the  Methods  for  Determining  their  Values, 
the  Tools,  Machines  and  Practical  Details  connected  with  an  intelli- 
gent and  a  profitable  prosecution  of  the  art,  -with  special  reference  to 
the  best  American  Practice.  To  which  are  added  a  History  of  Pa- 
per, complete  Lists  of  Paper-Making  Materials,  List  of  American 
Machines,  Tools  and  Processes  used  in  treating  the  Raw  Materials, 
and  in  Making,  Coloring  and  Finishing  Paper.  By  CHARLES  T. 
DAVIS.  Illustrated  by  156  engravings.  608  pages,  8vo.  $6.00 

DAVIS. — The  Manufacture  of  Leather: 

Being  a  Description  of  all  the  Processes  for  the  Tanning  and  Tawing 
with  Bark,  Extracts,  Chrome  and  all  Modern  Tannages  in  General 
Use,  and  the  Currying,  Finishing  and  Dyeing  of  Every  Kind  of  Leather; 
Including  the  Various  Raw  Materials,  the  Tools,  Machines,  and  all 
Details  of  Importance  Connected  with  an  Intelligent  and  Profitable 
Prosecution  of  the  Art,  with  Special  Reference  to  the  Best  American 
Practice.  To  which  are  added  Lists  of  American  Patents  ( 1884-1897) 
for  Materials,  Processes,  Tools  and  Machines  for  Tanning,  Currying, 
etc.  By  CHARLES  THOMAS  DAVIS.  Second  Edition,  Revised.' and 
in  great  part  Rewritten.  Illustrated  by  147  engravings  and  14  Sam- 
ples of  Quebracho  Tanned  and  Aniline  Dyed  Leathers,  8vo,  cloth, 
712  pages.  Price  ........  $7-5° 

DAWIDOWSKY— BRANNT.— A  Practical  Treatise  on  the 
Raw  Materials  and  Fabrication  of  Glue,  Gelatine,  Gelatine 
Veneers  and  Foils,  Isinglass,  Cements,  Pastes,  Mucilages, 
etc. : 

Based  upon  Actual  Experience.  By  F.  DAWIDOWSKY,  Technical 
Chemist.  Translated  from  the  German,  with  extensive  additions, 
including  a  description  of  the  most  Recent  American  Processes,  by 
WILLIAM  T.  BRANNT,  Graduate  of  the  Royal  Agricultural  College 
of  Eldena,  Prussia.  35  Engravings.  I2mo.  .  .  .  $2.50 

DE  GRAFF. — The  Geometrical  Stair-Builders'  Guide : 
being  a  Plain  Practical  System  of  Hand-Railing,  embracing  all  iti 
necessary  Details,  and  Geometrically  Illustrated  by  twenty-two  Steel 
Engravings;   together  with  the  use  of  the  most  approved  principle? 
of  Practical  Geometry.      By  SIMON  DE  GRAFF,  Architect      410. 

$2.CO 


HENRY   CAREY    BAIRD   &   CO.'S   CATALOGUE.        n 


DE  KONINCK— DIETZ.— A  Practical  Manual  of  Chemical 

Analysis  and  Assaying : 

A.S  applied  to  the  Manufacture  of  Iron  from  its  Ores,  and  to  Cast  Iron, 
Wrought  Iron,  and  Steel,  as  found  in  Commerce.  By  L.  L.  DH 
KoNiNCK,  Dr.  Sc.,  and  E.  DIETZ,  Engineer.  Edited  with  Notes,  by 
ROBERT  MALLET,  F.  R.  S.,  F.  S.  G.,  M.  I.  C.  E.,  etc.  American 
Edition,  Edited  with  Notes  and  an  Appendix  on  Iron  Ores,  by  A.  A. 
FESQUET,  Chemist  and  Engineer.  I2mo.  .  •  ;  «  $l~$Q 

DJNCAN.— Practical  Surveyor's  Guide: 

Containing  the  necessary  information  to  make  any  person  of  com* 
n'.on  capacity,  a  finished  land  surveyor  without  the  aid  of  a  teacher 
Bv  ANDREW  DUNCAN.  Revised.  72  engravings,  214 pp.  I2mo.  $1.50. 

DUPLAIS. — A  Treatise  on  the   Manufacture  and  Distillation 

of  Alcoholic  Liquors : 

Comprising  Accurate  and  Complete  Details  in  Regard  to  Alcohol 
from  Wine,  Molasses,  Beets,  Grnin,  Rice,  Potatoes,  Sorghum,  Aspho- 
del, Fitiits,  etc. ;  with  the  Distillation  and  Rectification  of  Brandy 
Whiskey,  Rum,  Gin,  Swiss  Absinthe,  etc.,  the  Preparation  of  Aro- 
matic Waters,  Volatile  Oils  or  Essences,  Sugars,  Syrups,  Aromatic 
Tinctures,  Liqueurs,  Cordial  Wines,  Effervescing  Wines,  etc.,  the 
Ageing  of  Brandy  .and  the  improvement  of  Spirits,  with  Copious 
Directions  and  Tables  for  Testing  and  Reducing  Spirituous  Liquors, 
etc.,  etc.  Translated  and  Edited  from  the  French  of  MM.  DUPLAIS, 
Aine  ft  Jeune.  By  M.  McKENNiE,  M.  D.  To  which  are  added  the 
United  States  Internal  Revenue  Regulations  for  the  Assessment  and 
Collection  of  Taxes  en  Distilled  Spirits.  Illustrated  by  fourteen 
folding  plates  and  several  wood  engravings.  743  pp.  8vo.  $12.50 

DUSSAUCE.— Practical  Treatise  on  the  Fabrication  of  Matches, 

Gun  Cotton,  and  Fulminating  Powder. 
By  Professor  H«  DUSSAUCE.     I2mo.          .... 

DYER  AND  COLOR-MAKER'S  COMPANION: 

Containing  upwards  of  two  hundred  Receipts  for  making  Colors,  on 
the  most  approved  princip'es,  for  all  the  various  styles  and  fabrics  now 
in  existence;  with  the  Scouring  Process,  and  plain  Directions  for 
Preparing,  Washing-off,  and  Finishing  the  Goods.  I2mo.  $1.00 

EDWARDS.— A  Catechism  of  the  Marine  Steam-Engine,  . 
For  the  use  of  Engineers.  Firemen,  and  Mechanics.  A  Practical 
Work  for  Practical  Men.  By  EMORY  EDWARDS,  Mechanical  Engi- 
neer. Illustrated  by  sixty-three  Engravings,  including  examples  <>f 
the  most  modern  Engines.  Third  edition,  thoroughly  revised,  with 
much  additional  matter.  12 mo.  414  pages  .  .  .  $2  or. 

EDWARDS. — Modern  American  Locomotive  Engines, 
Their  Design,  Construction  and  Management.     By  EMORY  EDWARDS. 
Illustrated  I2mo $2.00 

EDWARDS.— The  American  Steam  Engineer: 

Theoretical  and  Practical,  with  examples  of  the  latest  and  most  ap- 
proved American  practice  in  the  design  and  construction  of  Steam 
Engines  and  Boilers.  For  the  use  of  engineers,  machinists,  boiler- 
ipikers,  and  engineering  students.  By  EMORY  EDWARDS.  Fully 
illustrated,  419  pages.  I2mo.  •  .  .  .  $2.50 


12         HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 

EDWARDS.— Modern  American  Marine  Engines,  Boilers,  an* 

Screw  Propellers, 

Their  Design  and  Construction.  Showing  the  Present  Practice  ot 
the  most  Eminent  Engineers  and  Marine  Engine  Builders  in  the 
United  States.  Illustrated  by  30  large  and  elaborate  plates.  410.  $$.oc 

EDWARDS.— The  Practical  Steam  Engineer's  Guide 

In  the  Design,  Construction,  and  Management  of  American  Stationary. 
Portable,  and  Steam  Fire- Engines,  Steam  Pumps,  Boilers,  Injectors, 
Governors,  Indicators,  Pistons  and  Rings,  Safety  Valves  and  Steam 
Gauges.  For  the  use  of  Engineers,  Firemen,  and  Steam  Users.  B> 
EMORY  EDWARDS.  Illustrated  by  119  engravings.  420  pages. 
I2mo. $2  50 

EISSLER.— The  Metallurgy  of  Gold  : 

A  Practical  Treatise  on  the  Metallurgical  Treatment  of  Gold-Bear- 
ing  Ores,  including  the  Processes  of  Concentration  and  Chlorination, 
and  the  Assaying,  Melting,  and  Refining  of  Gold.  By  M.  EISSLER. 
With  132  Illustrations.  I2mo.  .....  $5.00 

EISSLER.— The  Metallurgy  of  Silver  : 

A  Practical  Treatise  on  the  Amalgamation,  Roasting,  and  Lixiviation 
of  Silver  Ores,  including  the  Assaying,  Melting,  and  Refining  of 
Silver  Bullion.  By  M.  EISSLER.  124  Illustrations.  336  pp. 
I2mo $425 

ELDER. — Conversations  on  the  Principal  Subjects  of  Political 

Economy. 
By  DR.  WILLIAM  ELDER.    8vo $2  50 

ELDER.— Questions  of  the  Day, 

Economic  and  Social.     By  DR.  WILLIAM  ELDER.     8vo.     .      $3.00 

ERNL— Mineralogy  Simplified. 

Easy  Methods  of  Determining  and  Classifying  Minerals,  including 
Ores,  by  means  of  the  Blowpipe,  and  by  Humid  Chemical  Analysis, 
based  on  Professor  von  Kobell's  Tables  for  the  Determination  of 
Minerals,  with  an  Introduction  to  Modern  Chemistry.  By  HENRY 
ERNI,  A.M.,  M.D.,  Professor  of  Chemistry.  Second  Edition,  rewritten, 
enlarged  and  improved.  I2mo.  ..... 

FAIRBAIRN.— The  Principles  of  Mechanism  and  Machinery 

of  Transmission  • 

Comprising  the  Principles  of  Mechanism,  Wheels,  and  Pullevs, 
Strength  and  Proportions  of  Shafts,  Coupling  of  Shafts,  and  Engag- 
ing  and  Disengaging  Gear.  By  SIR  WILLIAM  FAIRBAIRN,  Bait 
C.  E.  Beautifully  illustrated  by  over  150  wood-cuts.  In  one 
•volume.  I2mo  .  .  . $2.00 

FLEMING.— Narrow  Gauge  Railways  in  America. 
A  Sketch  of  their  Rise,  Progress,  and  Success.     Valuable  Statistics 
as  to  Grades,  Curves,  Weight  of  Rail,  Locomotives,  Cars,  etc.     By 
HOWARD  FLEMING.     Illustrated,  8vo $i  oa 

FORSYTH.— Book  of  Designs  for  Headstones,   Mural,  and 

oth&f  Monuments : 

Containing  78  Designs.  By  JAMES  FORSYTH.  With  an  Introduction 
by  CHARLES  BCUTELL,  M.  A.  4  to.,  cloth  .  .  • 


HENRY    CAREY    BAIRD   &   CO.'S   CATALOGUE.        '3 


FRANKEL — HUTTER. — A  Practical  Treatise  on  the  Manu* 
facture  of  Starch,  Glucose,  Starch-Sugar,  and  Dextrine: 

Based  on  the  German  of  LADISLAUS  VON  WAGNER,  Professor  in  the 
Royal  Technical  High  School,  Buda-Pest,  Hungary,  and  other 
authorities.  By  JULIUS  FRANKEL,  Graduate  of  the  Polytechnic 
School  of  Hanover.  Edited  by  ROBERT  HUTTER,  Chemist,  Practical 
Manufacturer  of  Starch-Sugar.  Illustrated  by  58  engravings,  cover- 
ing every  branch  of  the  subject,  including  examples  of  the  most 
Recent  and  Best  American  Machinery.  8vo.,  344  pp.  .  $3  50 

TARDNER. — The  Paintev's  Encyclopaedia: 
Containing  Definitions  of  a.l  Important  Words  in  the  Art  of  Plain 
and  Artistic  Painting,  with  Details  of  Practice  in  Coach,  Carriage, 
Railway  Car,  House,  Sign,  and  Ornamental  Painting,  including 
Graining,  Marbling,  Stnimng,  Varnishing,  Polishing,  Lettering, 
Stenciling,  Gilding,  Bronzing,  etc.  By  FRANKLIN  13.  GARDNER, 
158  Illustrations.  I2mo.  427  pp.  .  .  .  .  "  .  $2.00 

GARDNER. — Everybody's  Paint  Book: 

A  Complete  Guide  to  the  Art  of  Outdoor  and  Indoor  Painting,  De- 
signed for  the  Special  Use  of  those  who  wish  to  do  their  own  work, 
and  consisting  of  Practical  Lessons  in  Plain  Painting,  Varnishing, 
Polishing,  Staining,  P?prr  Hanging,  Kalsomining,  etc.,  as  well  as 
Directions  for  Renovating  Furniture,  and  Hints  on  Artistic  Work  for 
Home  Decoration.  38  Illustrations.  I2mc.,  183  pp.  .  ^$1.00 

GEE. — The  Goldsmith's  Handbook: 

Containing  full  instructions  for  the  Alloying  and  Working  of  Gold, 
including  the  Art  of  Alloying,  Melting,  Reducing,  Coloring,  Col 
lecting,  and  Refining;  the  Processes  of  Manipulation,  Recovery  of 
Waste;  Chemical  and  Physical  Properties  of  Gold;  with  a  New 
System  of  Mixing  its  Alloys ;  Solders,  Enamels,  and  other  Useful 
Rules  and  Recipes.  By  GEORGE  E.  GEE.  121110.  P  .  #1.25 

GEE. — The  Silversmith's  Handbook  : 

Containing  full  instructions  for  the  Alloying  and  Working  of  Silver, 
including  the  different  modes  of  Refining  -,nd  Melting  the  Metal;  its 
Solders;  the  Preparation  of  Imitation  Alloys;  Methods  of  Manipula- 
tion ;  Prevention  of  Waste  ;  Instructions  for  Improving  and  Finishing 
the  Surface  of  the  Work ;  together  with  other  Useful  Information  and 
Memoranda.  By  GEORGE  E.  GEE.  Illustrated.  I2mo.  £1.25 

GOTHIC  ALBUM  FOR  CABINET-MAKERS: 

Designs  for  Gothic  Furniture.     Twenty-three  plates.     Oblong  $1.50 

3RANT.  —  A  Handbook  on  the  Teeth  of  Gears  : 
Their  Curves,  Properties,  and  Practical  Construction.     By  GEORGK 
B.  GRANT.     Illustrated.     Third  Edition,  enlarged.     8vo.          $i  oo 

GREENWOOD.— Steel  and  Iron: 

Comprising  the  Practice  and  Theory  of  the  Several  Methods  Pur- 
sued in  their  Manufacture,  and  of  their  Treatment  in  the  Rolling. 
Mills,  the  Forge,  and  the  Foundry.  By  WILLIAM  HENRY  GREEN- 
WOOD, F.  C.  S.  With  97  Diagrams,  536  pages.  I2mo.  #2.00 


HENRY   CAREY    BAIRD   &   CO.'S   CATALOGUE. 


GREGORY.— Mathematics  for  Practical  Men : 

Adapted  to  the  Pursuits  of  Surveyors,  Architects,  Mechanics,  and 
Civil  Engineers.  By  OLINTHUS  GREGORY.  8vo.,  plates  $3.00 

GRISWOLD. — Railroad  Engineer's  Pocket  Companion  for  th< 

Field : 

Comprising  Rules  for  Calculating  Deflection  Distances  and  Angles, 
Tangential  Distances  and  Angles,  and  all  Necessary  Tables  for  En 
gineers;  also  the  Art  of  Levelling  from  Preliminary  Survey  to  the 
Construction  of  Railroads,  intended  Expressly  for  the  Young  En- 
gineer, together  with  Numerous  Valuable  Rules  and  Examples.  By 
W.  GRISWOLU.  I2mo.,  tucks  .....  $i.$o 

GRUNER.— Studies  of  Blast  Furnace  Phenomena: 

By  M.  L.  GRUNER,  President  of  the  General  Council  of  Mines  oi 
France,  and  lately  Professor  of  Metallurgy  at  the  Ecole  des  Mines. 
Translated,  with  the  author's  sanction,  with  an  Appendix,  by  L.  I). 
B.  GORDON,  F.  R.  S.  E.,  F.  G.  S.  8vo.  .  .  .  $2.50 

Hand-Book  of  Useful  Tables  for  the  Lumberman,  Farmei  and 

Mechanic: 

Containing  Accurate  Tables  of  Logs  Reduced  to  Inch  Board  Meas. 
ure,  Plank,  Scantling  and  Timber  Measure;  Wages  and  Rent,  by 
Week  or  Month;  Capacity  of  Granaries,  Bins  and  Cisterns;  Land 
Measure,  Interest  Tables,  with  Directions  for  Finding  the  Interest  on 
any  sum  at  4,  5,  6,  7  and  8  per  cent.,  and  many  other  Useful  Tables. 
32  mo.,  boards.  186  pages .25 

HASERICK.— The  Secrets  of  the  Art  of  Dyeing  Wool,  Cotton, 

and  Linen, 

Including  Bleaching  and  Coloring  Wool  and  Cotton  Hosiery  and 
Random  Yarns.  A  Treatise  based  on  Economy  and  Practice.  By 
E.  C.  HASERICK.  Illustrated  by  323  Dyed  Patterns  of  the  Yami 
or  fabrics.  8vo $7-5<3 

HATS  AND  FELTING: 

A  Practical  Treatise  on  their  Manufacture.  By  a  Practical  Hatter. 
Illustrated  by  Drawings  of  Machinery,  etc.  8vo.  .  .  $1.25 

HOFFER. — A    Practical   Treatise   on   Caoutchouc  and   Gulta 

Percha, 

Comprising  the  Properties  of  the  Raw  Materials,  and  the  manner  or 
Mixing  and  Working  them ;  with  the  Fabrication  of  Vulcanized  and 
Hard  Rubbers,  Caoutchouc  and  Gutta  Pescha  Compositions,  Water- 
proof Substances,  Elastic  Tissues,  the  Utilization  of  Waste,  etc.,  eu. 
From  the  German  of  RAIMUND  HOFFER.  By  W.  T.  BRANNT. 
Illustrated  I2mo.  .  $2.50 

HAUPT. — Street  Railway  Motors: 

With  Descriptions  and  Cost  of  Plants  and  Operation  of  the  Various 
Systems  how  in  Use.  I2mo.  .....  $1-75 


HENRY   CAREY   BAIRD   &   CO.'S  CATALOGUE.        15 

HAUPT— RHAWN.— A  Move  for  Better  Roads: 

Essays  on  Road-making  and  Maintenance  and  Road  Laws,  for 
which  Prizes  or  Honorable  Mention  were  Awarded  through  the 
University  of  Pennsylvania  by  a  Committee  of  Citizens  of  Philadel- 
phia, with  a  Synopsis  of  other  Contributions  and  a  Review  by  the 
Secretary,  LEWIS  M.  HAUPT,  A.  M.,  C.  E.;  also  an  Introduction  by 
WILLIAM  H.  RHAWN,  Chairman  of  the  Committee.  319  pages. 
8vo.  ..........  $2.oc 

HUGHES. — American  Miller  and  Millwright's  Assistant: 
By  WILLIAM  CARTER  HUGHES.     i2mo $1.50 

HULME. — Worked  Examination  Questions  in  Plane  Geomet- 
rical Drawing  : 

For  the  Use  of  Candidates  for  the  Royal  Military  Academy,  Wool- 
wich ;  the  Royal  Military  College,  Sandhurst ;  the  Indian  Civil  En- 
gineering College,  Cooper's  Hill ;  Indian  Public  Works  and  Tele- 
graph Departments ;  Royal  Marine  Light  Infantry ;  the  Oxford  and 
Cambridge  Local  Examinations,  etc.  By  F.  EDWARD  HULME,  F.  L. 
S.,  F.  S.  A.,  Art-Master  Marlborough  College.  Illustrated  by  300 
examples.  Small  quarto  ......  $2.  so 

JERVIS.— Railroad  Property: 

A  Treatise  on  the  Construction  and  Management  of  Railways; 
designed  to  afford  useful  knowledge,  in  the  popular  style,  to  the 
holders  of  this  class  of  property ;  as  well  as  Railway  Managers,  Offi- 
cers, and  Agents.  By  JOHN  B.  JERVIS,  late  Civil  Engineer  of  the 
Hudson  River  Railroad,  Croton  Aqueduct,  etc.  i2mo.,  cloth  $2.oc 

KEENE. — A  Hand-Book  of  Practical  Gauging: 

For  the  Use  of  Beginners,  to  which  is  added  a  Chapter  on  Distilla 
tion,  describing  the  process  in  operation  at  the  Custom-House  for 
ascertaining  the  Strength  of  Wines.  By  JAMES  B.  KEENE,  of  H.  M. 
Customs.  8vo.  ........  $1.00 

KELLEY.— Speeches,  Addresses,  and  Letters  on  Industrial  and 

Financial  Questions : 
By  Hox.  WILLIAM  D.  KELLEY,  M.  C.     544  pages,  8vo.  .        $2.50 

KELLOGG.— A  New  Monetary  System  : 

The  only  means  of  Securing  the  respective  Rights  of  Labor  and 
Property,  and  of  Protecting  the  Public  from  Financial  Revulsions. 
By  EDWARD  KELLOGG.  Revised  from  his  work  on  "Labor  and 
other  Capital."  With  numerous  additions  from  his  mnnuscript. 
Edited  by  MARY  KELLOGG  PUTNAM.  Fifth  edition.  To  which  i* 
added  a  Biographical  Sketch  of  the  Author.  One  volume,  I2mo. 

Paper  cover .         .         jgl.oo 

Bound  in  cloth 1.25 

KEMLO.— Watch-Repairer's  Hand-Book : 
Being  a  Complete  Guide  to  the  Young  Beginner,  in  Taking  Apart, 
Putting  Together,  and  Thoroughly  Cleaning  the  English  Lever  and 
other  .Foreign  Watches,  and  all  American  Watches.     By  F.  KEMLO, 
Practical  Watchmaker.     With  Illustrations.     I2mo.  .         $1.25 


i6          HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 

KENTISH.— A  Treatise  on  a  Box  of  Instruments, 

And  the  Slide  Rule ;  with  the  Theory  of  Trigonometry  and  Logs 
rit.hms,  including  Practical  Geometry,  Surveying,  Measuring  of  Tim 
her,  Cask  and  Malt  Gauging,  Heights,  and  Distances.  By  THOMA* 
KENTISH.  In  one  volume.  I2mo.  ....  $i.oc 

I  ERL.— The  Assayer's  Manual: 

An  Abridged  Treatise  on  the  Docimastic  Examination  of  Ores,  and 
Furnace  and  other  Artiticiil  Products.  By  BRUNO  KKRL,  Professor 
in  the  Roval  School  of  Mines.  Translated  from  the  German  by 
WILLIAM  T.  BRANNT.  Second  American  edition,  edited  with  Ex- 
tensive Additions  by  F.  LYNWOOD  GARRISON,  Member  of  the 
American  Institute  of  Mining  Engineers,  etc.  Illustrated  by  87  en- 
gravings. 8vo $3-OC 

KICK. -Flour  Manufacture. 

A  Treatise  on  Milling  Science  and  Practice.  By  FREDERICK  KICK 
Imperial  Regierungsrath,  Professor  of  Mechanical  Technology  in  tin. 
imperial  German  Polytechnic  Institute,  Prague.  Translated  from 
the  second  enlarged  and  revised  edition  with  supplement  by  H.  H. 
P.  POWLES,  Assoc.  Memb.  Institution  of  Civil  Engineers.  Illustrated 
with  28  Plates,  and  167  Wood-cuts.  367  pages.  8vo.  .  #10.00 
KINGZETT.— The  History,  Products,  and  Processes  of  the 

Alkali  Trade  : 

Including  the  most  Recent  Improvements.     By  CHARLES  THOMAS 
KINGZETT,  Consulting  Chemist.    With  23  illustrations.    8vo.       #2.50 
LANDRIN.— A  Treatise  on  Steel : 

Comprising  its  Theory,  Metallurgy,  Properties,  Practical  Working, 
and  Use.  By  M.  H.  C.  LANDRIN,  JR.  From  the  French,  by  A.  A. 

FESQUET.     i2mo.    .  $2.50 

LANGBEIN. — A    Complete  Treatise  on  the  Electro-Deposi- 

tion  of  Metals  : 

Comprising  Electro-Plating  and  Gnlvanoplastic  Operations,  the  De- 
position of  Metals  by  the  Contact  and  Immersion  Processes,  the  Color- 
ing of  Metals,  the  Methods  of  Grinding  and  Polishing,  as  well  as 
Descriptions  of  the  Electric  Elemenis,  Dynamo-Electric  Machines, 
Thermo- Piles  and  of  the  Materials  and  Processes  used  in  Every  De- 
partment of  the  Ait.  From  the  German  of  DR.  GEORGE  LANGBEIN, 
with  additions  by  WM.  T.  BRANNT.  Third  Edition,  thoroughly  re- 
vised and  much  enlarged.  150  Engravings.  520  pages.  8vo.  $4.00 

LARDNER.— The  Steam-Engine : 

Fof  the  Use  of  Beginners.     Illustrated.     I2mo.  75 

LEHNER.— The  Manufacture  of  Ink: 

Comprising  the  Raw  Materials,  and  the  Preparation  of  Wiling, 
Copying  and  Hektograph  Inks,  Safety  Inks,  Ink  Extracts  and  Pow- 
ders, etc.  Translated  from  the  German  of  SlGMUND  LEHNER,  with 
additions  by  WILLIAM  T.  BRANNT.  Illustrated.  12010. 


HENRY   CAREY    BAIRD   &   CO.'S   CATALOGUE.        17 

LARKIN. — The  Practical  Brass  and  Iron  Founder's  Guide: 
A  Concise  Treatise  on  Brass  Founding,  Moulding,  the  Metals  and 
their  Alloys,  etc. ;  to  which  are  added  Recent  Improvements  in  th« 
Manufacture  of  Iron,  Steel  by  the  Bessemer  Process,  etc.,  etc.  By 
TAMES  LARKIN,  late  Conductor  of  the  Brass  Foundry  Department  i& 
Reany,  Neafie  &  Co.'s  Penn  Works,  Philadelphia.  New  edition, 
revised,  with  extensive  additions.  I2mo.  .  .  .  $2.$& 

LEROUX. — A    Practical     Treatise    on    the    Manufacture    of 

Worsteds  and  Carded  Yarns  : 

Comprising  Practical  Mechanics,  with  Rules  and  Calculations  applied 
to  Spinning;  Sorting,  Cleaning,  and  Scouring  Wools;  the  English 
and  French  Methods  of  Combing,  Drawing,  and  Spinning  Worsteds, 
and  Manufacturing  Carded  Yarns.  Translated  from  the  French  of 
CHARLES  LEROUX,  Mechanical  Engineer  and  Superintendent  of  a 
Spinning-Mill,  by  HORATIO  PAINE,  M.  D.,  and  A.  A.  FESQUET, 
Chemist  and  Engineer.  Illustrated  by  twelve  large  Plates.  To  which 
is  added  an  Appendix,  containing  Extracts  from  the  Reports  of  the 
International  Jury,  and  of  the  Artisans  selected  by  the  Committee 
appointed  by  the  Council  of  the  Society  of  Arts,  London,  on  Woolen 
and  Worsted  Machinery  and  Fabrics,  as  exhibited  in  the  Paris  UnU 
versal  Exposition,  1867.  8vo.  .....  $5.00 

LEFFEL. — The  Construction  of  Mill-Dams : 
Comprising  also  the  Building  of  Race  and  Reservoir  Embankment* 
and  Head-Gates,  the   Measurement  of  Streams,  Gauging  of  Water 
Supply,  etc.     By  JAMES  LEFFEL  &  Co.    Illustrated  by  58  engravings. 
8vo. $2.50 

LESLIE. — Complete  Cookery: 

Directions  for  Cookery  in  its  Various  Branches.  By  Miss  LESLIE. 
Sixtieth  thousand.  Thoroughly  revised,  with  the  addition  of  New 
Receipts.  I2mo.  . $1.50 

LE  VAN. — The  Steam  Engine  and  the  Indicator : 

Their  Origin  and  Progressive  Development ;  including  the  Most 
Recent  Examples  of  Steam  and  Gas  Motors,  together  with  the  Indi- 
cator, its  Principles,  its  Utility,  and  its  Application.  By  WILLIAM 
BARNET  LE  VAN.  Illustrated  by  205  Engravings,  chiefly  of  Indi- 
cator-Cards. 469  pp.  8vo.  ......  $4.00 

LIEBER. — Assayer's  Guide  : 

Or,  Practical  Directions  to  Assayers,  Miners,  and  Smelters,  for  the 
Tests  and  Assays,  by  Heat  and  by  Wet  Processes,  for  the  Ores  of  all 
the  principal  Metals,  of  Gold  and  Silver  Coins  and  Alloys,  and  of 
Coal,  etc.  By  OSCAR  M.  LIEBER.  Revised.  283  pp.  I2mo.  $  1.50 

Lockwood's  Dictionary  of  Terms  : 

Used  in  the  Practice  of  Mechanical  Engineering,  embracing  those 
Current  in  the  Drawing  Office,  Pattern  Shop,  Foundry,  Fitting,  Turn- 
ing, Smith's  and  Boiler  Shops,  etc.,  etc.,  comprising  upwards  of  Six^ 
Thousand  Definitions.  Edited  by  a  Foreman  Pattern  Maker,  author 
tof  "  Pattern  Making."  417  pp.  I2tno.  .  .  .  $3.00 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE 


LUKIN.  —  Amongst  Machines: 

Embracing  Descriptions  of  the  various  Mechanical  Appliances  used 
in  the  Manufacture  of  Wood,  Metai,  and  other  Substances.  i2mo. 

#1.7* 
LUKIN.—  -The  Boy  Engineers  : 

What  They  Did,  and  How  They  Did  It.     With  30  plates.     i8mo. 

#i-75 

LUKIN.—  The  Young  Mechanic  t 

Practical  Carpentry.  Containing  Directions  for  the  Use  of  all  kinds, 
of  Tools,  and  for  Construction  of  Steam-  Engines  and  Mechanical 
Models,  including  the  Art  of  Turning  in  Wood  and  Metal.  By  JOHN 
LUKIN,  Author  of  "The  Lathe  and  Its  Uses,"  etc.  Illustrated. 
I2mo.  .  .  .  .  .  .  .  .  .  .  $i-75 

MAIN  and  BROWN.  —  Questions  on  Subjects  Connected  with 

the  Marine  Steam-Engine  : 

And  Examination  Papers;  with  Hints  for  their  Solution.  By 
THOMAS  J.  MAIN,  Professor  of  Mathematics,  Royal  Maval  College, 
and  THOMAS  BROWN,  Chief  Engineer,  R.  N.  I2mo.,  cloth  .  $1.00 

MAIN  and  BROWN.—  The  Indicator  and  Dynamometer: 
With  their  Practical  Applications  to  the  Steam-Engine.     By  THOMAS 
J.  MAIN,   M.  A.   F.  R.,   Ass't    S.    Professor    Royal    Naval   College, 
Portsmouth,  and  THOMAS  BROWN,  Assoc.  Inst.  C.  E.,  Chief  Engineei 
R.  N.,  attached  to  the  R.  N.  College.     Illustrated.     8vo.  . 

MAIN  and  BROWN.—  The  Marine  Steam-Engine. 

By  THOMAS  J.  MAIN,  F.  R.  Ass't  S.  Mathematical  Professor  at  the 
Royal  Naval  College,  Portsmouth,  and  THOMAS  BROWN,  Assoc. 
Inst.  C.  E.,  Chief  Engineer  R.  N.  Attached  to  the  Royal  Naval 
College.  With  numerous  illustrations.  8vo. 

MAKINS.—  A  Manual  of  Metallurgy: 

By  GEORGE  HOGARTH  MAKINS.  100  engravings.  Second  edition 
rewritten  and  much  enlarged.  I2mo.,  592  pages  .  .  $  3  .00 

MARTIN.  —  Screw-Cutting  Tables,  for  the  Use  of  Mechanica) 

Engineers  : 

Showing  the  Proper  Arrangement  of  Wheels  for  Cutting  the  Threads 
of  Screws  of  any  Required  Pitch;  with  a  Table  for  Making  the  Uni- 
versal Gas-Pipe  Thread  and  Taps.  By  W.  A.  MARTIN,  Engineer. 
8vo  ...........  50 

MICHELL.—  Mine  Drainage: 

Being  a  Complete  and  Practical  Treatise  on  Direct-Acting  Under* 
ground  Steam  Pumping  Machinery.  With  a  Description  of  a  large 
number  of  the  best  known  Engines,  their  General  Utility  and  ihe 
Special  Sphere  of  their  Action,  the  Mode  of  their  Application,  and 
their  Merits  compared  with  other  Pumping  Machinery.  By  STEPHEN 
MlCHELL.  Illustrated  by  137  engravings.  8vo.,  277  pages  .  &6.OG 

MOLESWORTH.—  Pocket-Book    of    Useful     Formulae     and 

Memoranda  for  Civil  and  Mechanical  Engineers. 
By  GUILFORD  L.  MOLESWORTH,  Member  of  the  Institution  of  Civil 
Engineers,  Chief  Resident  Engineer  of  the  Ceylon  Railway.     Full- 
in  Pocket-book  form      ......         £l.oo 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.          19 

MOORE.— The  Universal  Assistant  and  the  Complete  Me- 
chanic : 

Containing  over  one  million  Industrial  Facts,  Calculations,  Receipts^ 
Processes,  Trades  Secrets,  Rules,  Business  Forms,  Legal  Items,  Etc., 
in  every  occupation,  from  the  Household  to  the  Manufactory.  By 
R.  MOORE.  Illustrated  by  500  Engravings.  I2mo.  .  $2.50 

MORRIS. — Easy  Rules  for  the  Measurement  of  Earthworks  : 
By  means  of  the  Prismoidal  Formula.  Illustrated  with  Numerous 
Wood-Cuts,  Problems,  and  Examples,  and  concluded  by  an  Exten- 
sive Table  for  finding  the  Solidity  in  cubic  yards  from  Mean  Areas. 
The  whole  being  adapted  for  convenient  use  by  Engineers,  Surveyors, 
Contractors,  and  others  needing  Correct  Measurements  of  Earthwork. 

By  ELWOOD  MORRIS,  C.  E.    8vo $1.50 

MAUCHLINE.— The  Mine  Foreman's  Hand-Book 

Of  Practical  and  Theoretical  Information  on  the  Opening,  Venti- 
lating, and  Working  of  Collieries.  Questions  and  Answers  on  Prac- 
tical and  Theoretical  Coal  Mining.  Designed  to  Assist  Students  and 
Others  in  Passing  Examinations  for  Mine  Foremanships.  By 
ROBERT  MAUCHLINE,  Ex-Inspector  of  Mrnes.  A  New,  Revised  and 
Enlarged  Edition.  Illustrated  by  114  engravings.  8vo.  337 

Pages $3-75 

NAPIER.— A  System  of  Chemistry  Applied  to  Dyeing. 

By  JAMES  NAPIER,  F.  C.  S.  A  New  and  Thoroughly  Revised  Edi« 
tion.  Completely  brought  up  to  the  present  state  of  the  Science, 
including  the  Chemistry  of  Coal  Tar  Colors,  by  A.  A.  FESQUET, 
Chemist  and  Engineer.  With  an  Appendix  on  Dyeing  and  Calicq 
Printing,  as  shown  at  the  Universal  Exposition,  Paris,  1867.  Illus- 
trated. 8vo.  422  pages $3.00 

NEVILLE.— Hydraulic  Tables,  Coefficients,  and  Formulae,  foi 
finding  the  Discharge  of  Water  from  Orifices,  Notches, 
Weirs,  Pipes,  and  Rivers : 

Third  Edition,  with  Additions,  consisting  of  New  Formulae  for  the 
Discharge  from  Tidal  and  Flood  Sluices  and  Siphons;  general  infor- 
mation on  Rainfall,  Catchment-Basins,  Drainage,  Sewerage,  Water 
Supply  for  Towns  and  Mill  Power.  By  TOHN  NEVILLE,  C.  E.  M.  R 
I.  A. ;  Fellow  of  the  Royal  Geological  Society  of  Ireland.  Thicfc 

I2mo $5.50 

NEWBERY.— Gleanings     from     Ornamental    Art    of    every 

style : 

Drawn  from  Examples  in  the  British,  South  Kensington,   Indian, 
Crystal   Palace,  and  other   Museums,  the   Exhibitions  of  1851    and 
1862,  and  the  best  English  and  Foreign  works.     In  a  series  of  IOQ 
exquisitely  drawn   Plates,  containing  many  hundred  examples.     B* 
ROBERT  NEWBERY.    410.          .        .        .        .        .        .      $12.50 

NICHOLLS.  —The  Theoretical  and  Practical  Boiler-Maker  and 

Engineer's  Reference  Book: 

Containing  a  variety  of  Useful  Information  for  Employers  of  Labor 
Foremen  and  Working  Boiler- Makers,  Iron,  Copper,  and  Tinsmith* 


20        HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 

Oranghismen,  Engineers,  the  General  Steam-using  Public,  and  for  th« 
Use  of  Science  Schools  and  Classes.  By  SAMUEL  NICHOLLS.  Illus- 
trated by  sixteen  plates,  I2mo. $2.50 

NICHOLSON.— A  Manual  of  the  Art  of  Bookbinding : 

Containing  full  instructions  in  the  different  Branches  of  Forwarding, 
Gilding,  and  Finishing.  Also,  the  Art  of  Marbling  Book-edges  and 
Paper.  By  JAMES  B.  NICHOLSON.  Illustrated.  I2mo.,  cloth  $2.25 

NICOLLS.— The  Railway  Builder: 

A  Hand-Book  for  Estimating  the  Probable  Cost  of  American  Rail- 
way Construction  and  Equipment.  By  WILLIAM  J.  NICOLLS,  Civil 
Engineer.  Illustrated,  full  bound,  pocket-book  form 

NORM  ANDY.— The  Commercial  Handbook  of  Chemical  An- 
alysis : 

Or  Practical  Instructions  for  the  Determination  of  the  Intrinsic  oi 
Commercial  Value  of  Substances  used  in  Manufactures,  in  Trades, 
and  in  the  Arts.  By  A.  NORMANDY.  New  Edition,  Enlarged,  and 
to  a  great  extent  rewritten.  By  HENRY  M.  NOAD,  Ph.D.,  F.R.S., 
thick  I2mo.  .  $5.00 

N ORRIS. — A  Handbook  for  Locomotive   Engineers  and  Ma- 
chinists : 

Comprising  the  Proportions  and  Calculations  for  Constructing  Loco- 
motives; Manner  of  Setting  Valves;  Tables  cf  Squares,  Cubes,  Areas, 
etc.,  etc.  By  SEPTIMUS  NORRIS,  M.  E.  New  edition.  Illustrated, 
I2mo £1.50 

NYSTROM.— A  New  Treatise  on  Elements  of  Mechanics  : 
Establishing  Strict  Precision  in  the   Meaning  of  Dynamical  Terms : 
accompanied  with  an  Appendix  on  Duodenal  Arithmetic  and   Me 
trology.     By  JOHN  W.  NYSTROM,  C.  E.     Illustrated.     8vo.        $3.00 

NYSTROM. — On  Technological  Education  and  the  Construc- 
tion of  Ships  and  Screw  Propellers : 

For  Naval  and  Marine  Engineers.  By  JOHN  W.  NYSTROM,  Inte 
Acting  Chief  Engineer,  U.  S.  N.  Second  edition,  revised,  with  addi- 
tional matter.  Illustrated  by  seven  engravings.  I2mo.  .  $1-25 

O'NEILL. — A  Dictionary  of  Dyeing  and  Calico  Printing: 
Containing  a  brief  account  of  all  the  Substances  and  Processes  in 
use  in  the  Art  of  Dyeing  and  Printing  Textile  Fabrics  ;  with  Practical 
Receipts  and  Scientific  Information.  By  CHARLES  O'NEILL,  Analy- 
tical Chemist.  To  which  is  added  an  Essay  on  Coal  Tar  Colors  and 
their  application  to  Dyeing  and  Calico  Printing.  By  A.  A.  FESQUET, 
Chemist  and  Engineer.  With  an  appendix  on  Dyeing  and  Calico 
Printing,  as  shown  at  the  Universal  Exposition,  Paris,  1867-  8vo.. 
491  pages $3.00 

ORTON. — Underground  Treasures'. 

How  and  Where  to  P'ind  Them.  A  Key  for  the  Ready  Determination 
of  all  the  Useful  Minerals  within  the  United  States.  By  JAMES 
ORTON,  A.M.,  Late  Professor  of  Natural  History  in  Vassar  College, 
AJ.  Y.;  Cor.  Mem.  of  the  Academy  of  Natural  Sciences,  Philadelphia, 
and  of  the  Lyceum  of  Natural  History,  New  York ;  author  of  the 
"'Andes  and  the  Amazon,"  etc.  A  New  Edition,  with  Additions, 
illustrated $1.59 


HENRY    CAREY    BAIRD   &   CO.'S   CATALOGUE.        21 


OSBORN.— The  Prospector's  Field  Book  and  Guide. 

In  the  Search  For  and  the  Easy  Determination  of  Ores  and   Other 
Useful  Minerals.     By  Prof.  H.  S.  OSBORN,  LL.  D.     Illustrated  by  58 
Engravings.      I2mo.     Third  Edition.     Revised  ami  Enlarged  (1897). 

#1.50 

OSBORN— A  Practical  Manual  of  Minerals,  Mines  and  Min- 
ing: 

Comprising  the  Physical  Properties,  Geologic  Positions,  Local  Occur- 
rence and    Associations  of  the  Useful  Minerals;  their  Methods   of 
Chemical  Analysis  and  Assay  ;  together  with  Various  Systems  of  Ex- 
cavating and  limbering,  Brick  and  Masonry  Work,  during  Driving, 
Lining,  Bracing  and  other  Operations,  etc.     By  Prof.  H.  S.  OSBORN, 
LL.  D.,  Author  of  "  The  Prospector's  Field- Book  and  Guide."     171 
engravings.     Second  Edition,  revised.     8vo.      .    '     .         .         $4.50 
OVERMAN.— The  Manufacture  of  Steel: 

Containing  the  Practice  and  Principles  of  Working  and  Making  Steel. 
A  Handbook  for  Blacksmiths  and  Workers  in  Steel  and  Iron,  Wagon 
Makers,  Die  Sinkers,  Cutlers,  and  Manufacturers  of  Files  and  Hard- 
ware,  of  Slcel   and    Iron,  and  for   Men   of  Science  and  Art.     By 
FREDERICK  OVERMAN,  Mining  Engineer,  Author  of  the  "  Manu- 
facture of  Lon,"  etc.     A  new,  enlarged,  and   revised  Edition.     By 
A.  A.  FESQL,£T,  Chemist  and  Engineer.     I2mo.         .         .         $1.50 
OVERMAN.  -The  Moulder's  and  Founder's  Pocket  Guide  : 
A  Treatise  or.  Moulding  and  founding  in  Green-sand,  Dry -sand,  Loam, 
and  Cement;  the  Moulding  of  Machine  Frames,  Mill-gear,  Hollow- 
ware,  Ornaments,  Trinkets,  Bells,  and  Statues;  Description  of  Moulds 
for  Iron,  Bronze,  Brass,  and  other  Metals;   Plaster  of  Paris,  Sulphur, 
Wax,  etc. ;  the  Construction  of  Melting  Furnaces,  the  Melting  and 
Founding  of  Metals  ;  the  Composition  of  Alloys  and  their  Nature, 
etc.,  etc.     By   FREDERICK  OVERMAN,  M.  E.     A  new  Edition,  to 
which  is  added  a  Supplement  on  Statuary  and  Ornamental  Moulding, 
Ordnance,  Malleable  Iron  Castings,  etc.     By  A.  A.  FESQUET,  Chem- 
ist and  Engineer.     Illustrated  by  44  engravings.     I2mo.    .         $2.OO 
PAINTER,  GILDER,  AND  VARNISHER'S  COMPANION. 
Comprising  the  Manufacture  and  Test  of  Pigments,  the  Arts  of  Paint- 
ing, Graining,  Marbling,  Staining,  Sign- writing,  Varnishing,  Glass- 
staining,  and   Gilding  on  Glass;   together  with  Coach  Painting  and 
Varnishing,   and  the    Principles    of  the   Harmony  and  Contrast  of 
Colors.     Twenty-seventh  Edition.     Revised,  Enlarged,  and  in  great 
part  Rewritten.     By  WILLIAM  T.  BRANNT,  Editor  of  "Varnishes, 
Lacquers,  Printing  Inks  and  Sealing  Waxes."      Illustrated.     395  pp. 
I2mo.       ..........         $i  50 

PALLETT. — The  Miller's,  Millwright's, and  Engineer's  Guide. 
By  HENRY  PALLETT.     Illustrated.     i2mo.       .         .         .        #2.00 


22         HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 

PERCY.— The  Manufacture  of  Russian  Sheet-Iron. 

By  JOHN  PERCY,  M.  D.,  F.  R.  S.,  Lecturer  on  Metallurgy  at  the 
Royal  School  of  Mines,  and  to  The  Advance  Class  of  Artillery 
Officers  at  the  Royal  Artillery  Institution,  Woolwich ;  Author  of 
"  Metallurgy."  With  Illustrations.  8vo.,  paper  .  .  25  cts. 

PERKINS.— Gas  and  Ventilation  : 

Practical  Treatise  on  Gas  and  Ventilation.  With  Special  Relation 
to  Illuminating,  Heating,  and  Cooking  by  Gas.  Including  Scientific 
Helps  to  Engineer-students  and  others.  With  Illustrated  Diagrams. 
By  E.  E.  PERKINS.  I2mo.,  cloth $1.25 

PERKINS  AND  STOWE.— A  New  Guide  to  the  Sheet-iron 

and  Boiler  Plate  Roller  : 

Containing  a  Series  of  Tables  showing  the  Weight  of  Slabs  and  Pilei 
to  Produce  Boiler  Plates,  and  of  the  Weight  of  Piles  and  the  Sizes  of 
Bars  to  produce  Sheet-iron;  the  Thickness  of  the  Bar  Gauge 
in  decimals ;  the  Weight  per  foot,  and  the  Thickness,  on  the  Bar  or 
Wire  Gauge  of  the  fractional  parts  of  an  inch;  the  Weight  per 
sheet,  and  the  Thickness  on  the  Wire  Gauge  of  Sheet-iron  of  various 
dimensions  to  weigh  112  Ibs.  per  bundle;  and  the  conversion  of 
Short  Weight  into.  Long  Weight,  and  Long  Weight  into  Short. 
Estimated  and  collected  by  G.  H.  PERKINS  and  J.  G.  STOWE.  $1.50 

POWELL-CHANCE— HARRIS  —The    Principles  of  Glass 

Making. 

By  HARRY  J.  POWELL,  B.  A.  Together  with  Treatises  on  Crown  and 
Sheet  Glass;  by  HENRY  CHANCE,  M.  A.  And  Plate  Glass,  by  H. 
G.  HARRIS,  Asso.  M.  Inst.  C.  E.  Illustrated  i8mo.  .  $1.50 

PROCTOR. — A  Pocket-Book  of  Useful  Tables  and  Formulas 

for  Marine  Engineers : 

By  FRANK  PROCTOR.  Second  Edition,  Revised  and  Enlarged. 
Full -bound  pocket-book  form  ......  $1.50 

REGNAULT. — Elements  of  Chemistry: 

By  M.  V.  REGNAULT.  Translated  from  the  French  by  T.  FORREST 
BETTON,  M.  D.,  and  edited,  with  Notes,  by  JAMES  C.  BOOTH,  Melter 
and  Refiner  U.  S.  Mint,  and  WILLIAM  L.  FABER,  Metallurgist  and 
Mining  Engineer.  Illustrated  by  nearly  700  wood-engravings.  Com- 
prising nearly  1,500  pages.  In  two  volumes,  8vo.,  cloth  .  £6.00 

RICHARDS. — Aluminium : 

Its  History,  Occurrence,  Properties,  Metallurgy  and  Applications, 
including  its  Alloys.  By  JOSEPH  W.  RICHARDS,  A.  C.,  Chemist  and 
Practical  Metallurgist,  Member  of  the  Deutsche  Chemische  Gesell- 
schaft.  Illust.  Third  edition,  enlarged  and  revised  (1895)  •  #6.00 

RIFFAULT,  VERGNAUD,  and  TOUSSAINT.— A  Practical 

Treatise  on  the  Manufacture  of  Colors  for  Painting : 
Comprising  the  Origin,  Definition,  and  Classification  of  Colors;  the 
Treatment  of  the  Raw  Materials ;  the  best  Formulae  and  the  Newest 
Processes  for  the  Preparation  of  every  description  of  Pigment,  and 
the  Necessary  Apparatus  and  Directions  for  its  Use ;  Dryers ;  thd 
Testing,  Application,  and  Qualities  of  Paints,  etc.,  etc.  By  MM. 
RIFFAULT,  VERGNAUD,  and  TOUSSAINT.  Revised  and  Edited  by  M. 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.          23 

F.  MALEPEYRE.  Translated  from  the  French,  by  A.  A.  FESQtnriy 
Chemist  and  Engineer.  Illustrated  by  Eighty  engravings.  In  one 
vol.,  8vo.,  659  pages •  $$•&* 

ROPER.— A  Catechism  of  High- Pressure,  or  Non-Condensing 

Steam -Engines  : 

Including  the  Modelling,  Constructing,  and  Management  of  Steam- 
Engines  and  Steam  Boilers.  With  valuable  illustrations.  By  STE- 
PHEN ROPER,  Engineer.  Sixteenth  edition,  revised  and  enlarged. 
i8mo.,  tucks,  gilt  edge  .......  $2.00 

ROPER. — Engineer's  Handy-Book: 

Containing  a  full  Explanation  of  the  Steam-Engine  Indicator,  and  its 
Use  and  Advantages  to  Engineers  and  Steam  Users.  With  Formulae 
/or  Estimating  the  Power  of  all  Classes  of  Steam-Engines ;  also, 
Facts,  Figures,  Questions,  and  Tables  for  Engineers  who  wish  to 
qualify  Chemselves  for  the  United  States  Navy,  the  Revenue  Service, 
the  Mercantile  Marine,  or  to  take  charge  of  the  Better  Class  of  Sta- 
tionary Steam-Engines.  Sixth  edition.  l6mo.,  690  pages,  tucks, 
gilt  edge  ..........  $3-5° 

ROPER. — Hand-Book  of  Land  and  Marine  Engines  : 
Including  the  Modelling,  Construction,   Running,  and   Management 
of  Lane*  and  Marine  Engines  and  Boilers.     With  frustrations.     By 
STEPHEN  ROPER,  Engineer.    Sixth  edition.     I2mo.,tx'cks,  gilt  edge. 

$3-50 
ROPER.— Hand-Book  of  the  Locomotive  : 

Including  the  Construction  of  Engines  and  Boilers,  and  theConstruc- 
ti )  i,    Management,    and    Running   of  Locomotives.     By    STEPHEN 
ROPER.     Eleventh  edition.      l8mo.,  tucks,  gilt  edge  .         $2.50 

ROPER. — Hand-Book  of  Modern  Steam  Fire-Engines. 

With  illustrations.     By  STEPHEN  ROPER,  Engineer.     Fourth  edition, 
1 2ino.,  tucks,  gilt  edge       .......         $3'$<3 

ROPER. — Questions  and  Answers  for  Engineers. 
This  little   book  contains  all   the  Questions  that  Engineers  will  be 
asked  when  undergoing  an  Examination  for  the  purpose  of  procuring 
Licenses,  and  they  are  so  plain  that  any  Engineer  or  Fireman  of  or 
dinary  intelligence  may  commit  them  to  memory  in  a  short  time..    By 
STEPHEN  ROPER,  Engineer.     Third  edition        .         .         .         $2.00 
ROPER. — Use  and  Abuse  of  the  Steam  Boiler. 
By  STEPHEN   ROPER,  Engineer.     Eighth  edition,  with  illustrations. 

i8mo.,  tucks,  gilt  edge $2.00 

ROSE. — The  Complete  Practical  Machinist : 

Embracing  Lathe  Work,  Vise  Work,  Drills  and  Drilling,  Taps  and 
Dies,  Hardening  and  Tempering,  the  Making  and  Use  of  Tools. 
Tool  Grinding,  Marking  out  Work,  Machine  Tools,  etc.  By  JOSHUA 
ROSE.  39^  Engravings.  Nineteenth  Edition,  greatly  Enlarged  with 
New  and  Valuable  Matter.  I2mo.,  504  pages.  .  .  $2.50 
ROSE. — Mechanical  Drawing  Self-Taught: 

Comprising  Instructions  in  the  Selection  and  Preparation  of  Drawing 
Instruments,  Elemental v  Instruction   in   Practical  Mechanical  Draw- 


24         HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 

ing,  together  with  Examples  in  Simple  Geometry  and  Elementary 
Mechanism,  including  Screw  Threads,  Gear  Wheels,  Mechanical 
Motions,  Engines  and  Boilers.  By  JOSHUA  ROSE,  M.  E.  Illustrated 
by  330  engravings.  8vo.,  313  pages  ....  #4.00 

ROSE.— The  Slide- Valve  Practically  Explained: 

Embracing  simple  and  complete  Practical  Demonstrations  of  th, 
operation  of  each  element  in  a  Slide-valve  Movement,  and  illustrat- 
ing the  effects  of  Variations  in  their  Proportions  by  examples  care- 
fully  selected  from  the  most  recent  and  successful  practice.  By 
JOSHUA  ROSE,  M.  E.  Illustrated  by  35  engravings  .  $1.00 

ROSS. — The  Blowpipe  in  Chemistry,  Mineralogy  and  Geology : 
Containing  all  Known  Methods  of  Anhydrous  Analysis,  many  Work- 
ing Examples,  and  Instructions  for  Making  Apparatus.  By  LIEUT.- 
COLONEL  W.  A.  Ross,  R.  A.,  F.  G.  S.  With  120  Illustrations. 
I2mo $2.00 

SHAW.— Civil  Architecture : 

Being  a  Complete  Theoretical  and  Practical  System  of  Building,  con. 
taining  the  Fundamental  Principles  of  the  Art.  By  EDWARD  SHAW, 
Architect.  To  which  is  added  a  Treatise  on  Gothic  Architecture,  etc. 
By  THOMAS  W.  SILLOWAY  and  GEORGE  M.  HARDING,  Architects. 
The  whole  illustrated  by  102  quarto  plates  finely  engraved  on  copper. 
Eleventh  edition.  4to.  .......  #6.00 

SHUNK. — A  Practical  Treatise  on  Railway  Curves  and  Loca- 
tion, for  Young  Engineers. 
By  W.  F.  SHUNK,  C.  E.    I2mo.    Full  bound  pocket-book  form  $2.00 

SLATER. — The  Manual  of  Colors  and  Dye  Wares. 
By  J.  W.  SLATER.     I2mo $3.00 

SLOAN. — American  Houses  : 

A  variety  of  Original  Designs  for  Rural  Buildings.  Illustrated  by 
26  colored  engravings,  with  descriptive  references.  By  SAMUEL 
SLOAN,  Architect.  8vo.  .  .  .  .  .  .  $ i.oo 

SLOAN. — Homestead  Architecture: 

Containing  Forty  Designs  for  Villas,  Cottages,  and  Farm-houses,  with 
Essays  on  Style,  Construction,  Landscape  Gardening,  Furniture,  etc., 
etc.  Illustrated  by  upwards  of  200  engravings.  By  SAMUEL  SLOAN, 
Architect.  8vo $3.00 

SLOANE.— Hoir>e  Experiments  m  Science. 

By  T.  O'CoNOR  SLOANE,  E.  M.,  A.  M.,  Fh.  D.  Illustrated  by  91 
engravings.  I2mo.  .......  $l.oo 

SMEATON.— Builder's  Pocket-Companion : 

Containing  the  Elements  of  Building,  Surveying,  and  Architecture; 

with  Practical  Rules  and  Instructions  connected  with  the  subject. 

By  A.  C.  SMEATON,  Civil  Engineer,  etc.     12010.       .  75  cts. 

SMITH.— A  Manual  of  Political  Economy. 

By  E.  PESHINE  SMITH.    A  New  Edition,  to  which  is  added  a  full 

Index.     i2mo.          .        . $125 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.          25 

SMITH. — Parks  and  Pleasure -Grounds : 

Or  Practical  Notes  on  Country  Residences,  Villas,  Public  Parks,  and 
Gardens.  By  CHARLES  H.  J.  SMITH,  Landscape  Gardener  and 
Garden  Architect,  etc.,  etc.  I2mo.  ....  $2.oa 

SMITH.— The  Dyer's  Instructor : 

Comprising  Practical  Instructions  in  the  Art  of  Dyeing  Silk,  Cotton^ 
Wool,  and  Worsted,  and  Woolen  Goods;  containing  nearly  800 
Receipts.  To  which  is  added  a  Treatise  on  the  Art  of  Padding;  anc} 
the  Printing  of  Silk  Warps,  Skeins,  and  Handkerchiefs,  and  the 
various  Mordants  and  Colors  for  the  different  styles  of  such  work. 
By  DAVID  SMITH,  Pattern  Dyer.  I2mo.  .  .  .  $1.50 

SMYTH.— A  Rudimentary  Treatise  on  Coal  and  Coal-Mining. 
By  WARRINGTON  W.  SMYTH,  M.  A.,  F.  R.  G.,  President  R.  G.  S, 
of  Cornwall.  Fifth  edition,  revised  and  corrected.  With  numer- 
ous illustrations.  I2mo.  ......  $i«7$ 

SNIVELY.— Tables  for  Systematic  Qualitative  Chemical  AnaK 

ysis. 
By  JOHN  H.  SNIVELY,  Phr.  D.     8vo.        .        . "      .        .        $1.00 

SNIVELY.— The  Elements  of  Systematic  Qualitative  chemical 

Analysis : 

A  Hand-book  for  Beginners.    By  JOHN  H.  SNIVELY,  Phr.  D.    i6mo. 

$2.00 

STOKES.— The  Cabinet  Maker  and  Upholsterer's  Companion: 
Comprising  the  Art  of  Drawing,  as  applicable  to  Cabinet  Work; 
Veneering,  Inlaying,  and  Buhl- Work;  the  Art  of  Dyeing  and  Stain- 
ing Wood,  Ivory,  Bone,  Tortoise-Shell,  etc.  Directions  for  Lacker- 
ing, Japanning,  and  Vanishing;  to  make  French  Polish,  Glues, 
Cements,  and  Compos-l.Fns;  with  numerous  Receipts,  useful  to  work 
men  generally.  Bv  STOKES.  Illustrated.  A  New  Edition,  with 
an  Appendix  upor  ,ench  Polishing,  Staining,  Imitating,  Varnishing, 
etc.,  etc.  I2mo  ........  $1.25 

STRENGTH  AND  OTHER  PROPERTIES  OF  METALS; 
Reports  of  Experiments  on  the  Strength  and  other  Properties  of 
Metals  for  Cannon.  With  a  Description  of  the  Machines  for  Testing 
Metals,  and  of  the  Classification  of  Cannon  in  service.  By  Officers 
of  the  Ordnance  Department,  U.  S.  Army.  By  authority  of  the  Secre- 
tary  of  War.  Illustrated  by  25  large  steel  plates.  Quarto  .  $5.00 

BULLIVAN.— Protection  to  Native  Industry. 
By  Sir  EDWARD  SULLIVAN,  Baronet,  author  of  "  Ten  Chapters  on 
Social  Reforms."     8vo #1.00 

BULZ. — A  Treatise  on  Beverages  : 

Or  the  Complete  Practical  Bottler.  Full  instructions  for  Laboratory 
Work,. with  Original  Practical  Recipes  for  all  kinds  of  Carbonated 
Drinks,  Mineral  Waters,  Flavorings,  Extracts,  Syrups,  etc.  By 
CHAS.  HERMAN  SULZ,  Techhical  Chemist  ana  Practical  Bottler 
Illustrated  by  428  Engraving*.  8ttf  pp.  £vo  .  *  $10.00 


26         HENRY  CAREY  BAIRb  &  CO.'S  CATALOGUE. 


SYME. — Outlines  of  an  Industrial  Science. 
By  DAVID  SYME.     i2mo.  .  ...        $2.00 

TABLES     SHOWING     THE     WEIGHT     OF     ROUND, 

SQUARE,  AND  FLAT  BAR  IRON,  STEEL,  ETC., 
By  Measurement.     Cloth  ......  63 

TAYLOR.— Statistics  of  Coal : 

Including  Mineral  Bituminous  Substances  employed  in  Arts  and 
Manufactures;  with  their  Geographical,  Geological,  and  Commercial 
Distribution  and  Amount  of  Production  and  Consumption  on  the 
American  Continent.  With  Incidental  Statistics  of  the  Iron  Manu- 
facture. By  R.  C.  TAYLOR.  Second  edition,  revised  by  S.  S.  HALDE- 
MAN.  Illustrated  by  five  Maps  and  many  wood  engravings.  8vo., 
cloth $6.00 

TEMPLETON.— The  Practical  Examinator  on  Steam  and  the 

Steam -Engine : 

With  Instructive  References  relative  thereto,  arranged  for  the  Use  of 
Engineers,  Students,  and  others.  By  WILLIAM  TEMPLETON,  En- 
gineer.  I2mo.  ........  $1.00 

THAU  SING.— The  Theory  and  Practice  of  the  Preparation  of 

Malt  and  the  Fabrication  of  Beer : 

With  especial  reference  to  the  Vienna  Process  of  Brewing.  Elab- 
orated from  personal  experience  by  JULIUS  E.  THAUSING,  Professor 
at  the  School  for  Brewers,  and  at  the  Agricultural  Institute,  Modling, 
near  Vienna.  Translated  from  the  German  by  WILLIAM  T.  BRANNT, 
Thoroughly  and  elaborately  edited,  with  much  American  matter,  and 
according  to  the  latest  and  most  Scientific  Practice,  by  A.  SCHWARZ 
and  DR.  A.  II.  BAUER.  Illustrated  by  140  Engravings.  8vo.,  815 
pages  ..........  $10.00 

THOMAS. — The  Modern  Practice  of  Photography: 

By  R.  W.  THOMAS,  F.  C.  S.    8vo.  ....  25 

THOMPSON.— Political  Economy.     With  Especial  Reference 

fo  the  Industrial  History  of  Nations  : 

By  ROBERT  E.  THOMPSON,  M.  A.,  Professor  of  Social  Science  in  the 
University  of  Pennsylvania.  I2mo.  .  .  .  .  $1.50 

THOMSON. — Freight  Charges  Calculator: 
By  ANDREW  THOMSON,  Freight  Agent.     24010.        .        .        $1.25 

TURNER'S  (THE)  COMPANION: 

Containing  Instructions  in  Concentric,  Elliptic,  and  Eccentric  Turn, 
hig;  also  various  Plates  of  Chucks,  Tools,  and  Instruments;  and 
Directions  for  using  the  Eccentric  Cutter,  Drill,  Vertical  Cutter,  and 
Circular  Rest;  with  Patterns  and  Instructions  for  working  them 
I2mo. #I.oo 

TURNING :   Specimens  of  Fancy  Turning   Executed  on  the 

Hand  or  Foot- Lathe : 

With  Geometric,  Oval,  and  Eccentric  Chucks,  and  Elliptical  Cutting 
Frame.  By  an  Amateur.  Illustrated  by  30  exquisite  Photographs. 
4*o. $2.50 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 


VAILE. — Galvanized- Iron  Cornice-Worker's  Manual: 

Containing  Instructions  in  Laying  out  the  Different  Mitres,  and 
Making  Patterns  for  all  kinds  of  Plain  and  Circular  Work.  Also» 
Tables  of  Weights,  Areas  and  Circumferences  of  Circles,  and  other 
Matter  calculated  to  Benefit  the  Trade.  By  CHARLES  A.  VAILE. 
Illustrated  by  twenty-one  plates.  4to.  .  .  V  '  .  $S-°° 

VILLE. — On  Artificial  Manures  : 

Their  Chemical  Selection  and  Scientific  Application  to  Agriculture. 
A  series  of  Lectures  given  at  the  Experimental  Farm  at  Vincennes, 
during  1867  and  1874-75.  By  M.  GEORGES  VILLE.  Translated  and 
Edited  by  WILLIAM  CROOKES,  F.  R.  S.  Illustrated  by  thirty-one 
engravings.  8vo.,  450  pages  .  .  ...  . :  $6.00 

VILLE. — The  School  of  Chemical  Manures  : 
Or,  Elementary  Principles  in  the  Use  of  Fertilizing  Agents.     From 
the  French  of  M.  GEO.  VILLE,  by  A.  A.  FESQUET,  Chemist  and  En- 
gineer.    With  Illustrations.     I2mo.  ....         $1.25 

VOGDES.— The  Architect's  and  Builder's  Pocket- Companion 

and  Price-Book : 

Consisting  of  a  Shoit  but  Comprehensive  Epitome  of  Decimals,  Duo- 
decimals, Geometry  and  Mensuration ;  with  Tables  of  United  States 
Measures,  Sizes,  Weights,  Strengths,  etc.,  of  Iron,  Wood,  Stone, 
Brick,  Cement  and  Concretes,  Quantities  of  Materials  in  given  Sizes 
and  Dimensions  of  Wood,  Brick  and  Stone;  and  full  and  complete 
Bills  of  Prices  for  Carpenter's  Work  and  Painting ;  also,  Rules  for 
Computing  and  Valuing  Brick  and  Brick  Work,  Stone  Work,  Paint- 
ing, Plastering,  with  a  Vocabulary  of  Technical  Terms,  etc.  By 
FRANK  W.  VOGDES,  Architect,  Indianapolis,  Ind.  Enlarged,  revised, 
and  corrected.  In  one  volume,  368  pages,  full-bound,  pocket-book 

form,  gilt  edges $2.00 

Cloth         .  1.50 

VAN  CLEVE.— The  English  and  American  Mechanic : 

Comprising  a  Collection  of  Over  Three  Thousand  Receipts,  Rules, 
and  Tables,  designed  for  the  Use  of  every  Mechanic  and  Manufac- 
turer. By  B.  FRANK  VAN  CLEVE.  Illustrated.  500  pp.  121110.  $2.00 

WAHNSCHAFFE.— A  Guide  to  the  Scientific  Examination 

of  Soils : 

Comprising  Select  Methods  of  Mechanical  and  Chemical  Analysii 
and  Physical  Investigation.  Translated  from  the  German  of  Dr.  F. 
WAHNSCHAFFE.  With  additions  by  WILLIAM  T.  BRANNT.  Illus. 
trated  by  25  engravings.  I2mo.  177  pages  .  .  .  $1.50 

WALL. — Practical  Graining : 

With  Descriptions  of  Colors  Employed  and  Tools  Used.  Illustrated 
by  47  Colored  Plates,  Representing  the  Various  Woods  Used  JK 
Interior  Finishing.  By  WILLIAM  E.  WALL.  8vo.  .  $2.$o 

WALTON. — Coal-Mining  Described  and  Illustrated: 
By  THOMAS  H.  WALTON,  Mining  Engineer.    Illustrated  by  24  large 
and  elaborate  Plates,  after  Actual  Workings  and  Apparatus.      #5.oc 


a8         HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 

WARE.— The  Sugar  Beet. 

Including  a  History  of  the  Beet  Sugar  Industry  in  Europe,  Varietier 
of  the  Sugar  Beet,  Examination,  Soils,  Tillage,  Seeds  and  Sowing 
Yield  and  Cost  of  Cultivation,  Harvesting,  Transportation,  Conserva- 
tion, Feeding  Qualities  of  the  Beet  and  of  the  Pulp,  etc.  By  LEWII 
S.  WARE,  C.  E.,  M.  E.  Illustrated  by  ninety  engravings.  8vo. 

$4.09 

WARN.— The  Sheet-Metal  Worker's  Instructor: 

For  Zinc,  Sheet-Iron,  Copper,  and  Tin-Plate  Workers,  etc.  Contain- 
ing a  selection  of  Geometrical  Problems ;  also,  Practical  and  Simple- 
Rules  for  Describing  the  various  Patterns  required  in  the  different 
branches  of  the  above  Trades.  By  REUBEN  H.  WARN,  Practical 
Tin-Plate  Worker.  To  which  is  added  an  Appendix,  containing 
Instructions  for  Boiler-Making,  Mensuration  of  Surfaces  and  Solids, 
Rules  for  Calculating  the  Weights  of  different  Figures  of  Iron  and" 
Steel,  Tables  of  the  Weights  of  Iron,  Steel,  etc.  Illustrated  by  thirty- 
two  Plates  and  thirty-seven  Wood  Engravings.  8vo.  .  $3.00 

WARNER. — New  Theorems,  Tables,  and  Diagrams,  for  the* 
Computation  of  Earth-work : 

Designed  for  the  use  of  Engineers  in  Preliminary  and  Final  Estimates 
of  Students  in  Engineering,  and  of  Contractors  and  other  non-profes- 
sional Computers.  In  two  parts,  with  an  Appendix.  Part  I.  A  Prac- 
tical Treatise ;  Part  II.  A  Theoretical  Treatise,  and  the  Appendix. 
Containing  Notes  to  the  Rules  and  Examples  of  Part  I.;  Explana- 
tions of  the  Construction  of  Scales,  Tables,  and  Diagrams,  and  a. 
Treatise  upon  Equivalent  Square  Bases  and  Equivalent  Level  Heights. 
The  whole  illustrated  by  numerous  original  engravings,  comprising, 
explanatory  cuts  for  Definitions  and  Problems,  Stereometric  Scales 
and  Diagrams,  and  a  series  of  Lithographic  Drawings  from  Models  i 
Showing  all  the  Combinations  of  Solid  Forms  which  occur  in  Railroad 
Excavations  and  Embankments.  By  JOHN  WARNER,  A.  M.,  Mining- 
and  Mechanical  Engineer.  Illustrated  by  14  Plates.  A  new,  revised 
and  improved  edition.  8vo. $4«OC 

WATSON.— A  Manual  of  the  Hand-Lathe  : 

Comprising  Concise  Directions  for  Working  Metals  of  all  kinds, 
Ivory,  Bone  and  Precious  Woods;  Dyeing,  Coloring,  and  French 
Polishing;  Inlaying  by  Veneers,  and  various  methods  practised  to 
produce  Elaborate  work  with  Dispatch,  and  at  Small  Expense.  By 
EGBERT  P.  WATSON,  Author  of  "  The  Modern  Practice  of  American 
Machinists  and  Engineers."  Illustrated  by  78  engravings.  $1.50 

WATSON. — The  Modern  Practice  of  American  Machinists  and 

Engineers 

Including  the  Construction,  Application,  and  Use  of  Drills,  Lathe 
Tools,  Cutters  for  Boring  Cylinders,  and  Hollow-work  generally ,  with 
the  most  Economical  Speed  for  the  same ;  the  Results  verified  bj, 
Actual  Practice  at  the  Lathe,  the  Vise,  and  on  the  Floor.  Together 


HENRY   CAREY    BAIRD   &   CO.'S   CATALOGUE.         29 


\vith  Workshop  Management,  Economy  of  Manufacture,  the  Steam 
Engine,  Boilers,  Gears,  Belting,  etc.,  etc.  By  EGBERT  P.  WATSON. 
1 1  lustra1  ed  by  eighty-six  engravings.  I2mo.  .  .  .  $2.50 

WATT.— The  Art  of  Soap  Making  : 

A  Practical  Hand-Book  ot  the  Manufacture  of  Hard  and  Soft  Soaps, 
Toilet  Soaps,  etc.  Fifth  Edition,  Revised,  to  which  is  added  an 
Appendix  on  Modern  Candle  Making.  By  ALEXANDER  WATT. 
111.  I2mo.  .........  $3.00 

WEATHERLY. — Treatise  on  the  Art  of  Boiling  Sugar,  Crys- 
tallizing, Lozenge-making,  Comfits,  Gum  Goods, 
And  other  processes  for  Confectionery,  etc.,  in  which  are,  explained, 
in  an  easy  and  familiar  manner,  the  various  Methods  of  Manufactur- 
ing every  Description  of  Raw  and  Refined  Sugar  Goods,  as  sold  by 
Confectioners  and  others.  I2mo.  .....  $1.50 

\\' ILL.— Tables  of  Qualitative  Chemical  Analysis  : 

\\  uh  an  Introductory  Chapter  on  the  Course  of  analysis.  By  Pro- 
fessor HEINRICH  WILL,  of  Giessen,  Germany.  Third  American, 
from  the  eleventh  German  edition.  Edited  by  CHARLES  F.  HIMES, 
Ph.  D.,  Professor  of  Natural  Science,  Dickinson  College,  Carlisle, 
Pa.  8vo #1.50 

'WILLIAMS.— On  Heat  and  Steam  : 

Embracing  New  Views  of  Vaporization,  Condensation  and  Explo- 
.sion.  By  CHARLES  WYE  \Vn  LIAMS,  A.  I.  C.  E.  Illustrated.  8vo. 

$2.50 

"WILSON. — First  Principles  of  Political  Economy: 

With  Reference  to  Statesmanship  and  the  Progress  of  Civilization. 
By  Professor  W.  D.  WILSON,  of  the  Cornell  University.  A  new  and 
revised  edition.  I2mo.  .  .  .  .  .  .  .  $l-S° 

'WILSON.— The  Practical  Tool  Maker  and  Designer: 

Comprising  a  Full  Description  of  the  Latest  Construction  of  Tools 
and  Fixtures  for  Modern  Machine  Tools.  By  H.  S.  WILSON.  Illus- 
trated by  about  250  Engravings.  8vo.  .  .  .  .  $2  50 
The  work  is  designed  to  be  an  exnos6  of  the  latest  methods  for  the 
manufacture  of  metal  goods;  and  a  treatise  on  fitting  the  proper 
tools  to  modern  metal-working  machinery  for  the  uniform  production 
of  interchangeable  work.  It  includes,  among  others,  the  following 
subjects:  Use  and  abuse  of  files;  Die  making  for  the  punching  and 
cutting  press,  with  illustrations  of  dies  for  completing  complicate  i 
pieces  at  one  stroke  of  the  press ;  Tools  for  making  buttons  with  as- 
sembling attachments;  Coining;  Embossing;  Cartridge  making;  Hol- 
lowware  ;  Screw  Machines;  Bolt  and  rivet  headers;  Tapping  machines; 
System  of  making  gauges;  Drop  forging;  Manufacture  of  wire;  The 
drawing  of  brazed  and  seamless  tubing,  and  the  possibilities  of  the 
draw  bench;  The  Fox  lathe;  Brazing  fixtures;  Pickling  and  cleaning 
conveniences;  Reamers;  Taps;  Dies;  Jigs;  Milling  machine  fixtures; 
Shop  secrets,  etc. 

'WOODS. — Compound  Locomotives: 

By  ARTHUR  TANNATT  WOODS.  Second  edition,  revised  and  enlarged 
by  DAVID  LEONARD  BARNES,  A.  M.,  C.  E.  8vo.  330  pp.  $3.00 


30        HENRY   CAREY   BAIRD  &   CO.'S  CATALOGUE. 

WOHLER.— A  Hand-Bookof  Mineral  Analysis: 

By  F.  WOHLER,  Professor  of  Chemistry  in  the  University  of  Gottin- 
gen.  Edited  by  HENRY  B.  NASON,  Professor  of  Chemistry  in  the 
Renssalaer  Polytechnic  Institute,  Troy,  New  York.  Illustrated. 
I2mo $2.50 

WORSSAM.— On  Mechanical  Saws: 

From  the  Transactions  of  the  Society  of  Engineers,  1869.  By  S.  W. 
WORSSAM,  JR.  Illustrated  by  eighteen  large  plates.  8vo.  $1.50 

RECENT   ADDITIONS. 

BRANNT. — Varnishes,  Lacquers,  Printing  Inks  and  Sealing  - 
Waxes : 

Their  Raw  Materials  and  their  Manufacture,  to  which  is  added  the 
Art  of  Varnishing  and  Lacquering,  including  the  Preparation  of  Put- 
ties and  of  Stains  for  Wood,  Ivory,  Bone,  Horn,  and  Leather.  By 
WILLIAM  T.  BRANNT.  Illustrated  by  39  Engravings,  338  pages. 

I2tno $3.00 

BRANNT — The  Practical  Scourer  and  Garment  Dyer: 

Comprising  Dry  or  Chemical  Cleaning ;  the  Art  of  Removing  Stains , 
Fine  Washing;  Bleaching  and  Dyeing  of  Straw  Hats,  Gloves,  and 
Feathers  of  all  kinds;  Dyeing  of  Worn  Clothes  of  all  fabrics,  in- 
cluding Mixed  Goods,  by  One  Dip;  and  the  Manufacture  of  Soaps 
and  Fluids  for  Cleansing  Purposes.  Edited  by  WILLIAM  T.  BRANNT, 
Editor  of  "The  Techno-Chemical  Receipt  Book."  Illustrated. 
203  pages.  I2mo.  .,.....'  $2.00 

BRANNT.— Petroleum . 

Its  History,  Origin,  Occurrence,  Production,  Physical  and  Chemical 
Constitution,  Technology,  Examination  and  Uses;  Together  with 
the  Occurrence  and  Uses  of  Natural  Gas.  Edited  chiefly  from  the 
German  of  Prof.  Hans  Hoefer  and  Dr.  Alexander  Veith,  by  WM. 
T.  BRANNT.  Illustrated  by  3  Plates  and  284  Engravings.  743  pp. 
8vo.  #7-50 

BRANNT. — A  Practical  Treatise  on  the  Manufacture  of  Vine- 
gar and  Acetates,  Cider,  and  Fruit- Wines  : 
Preservation  of  Fruits  and  Vegetables  by  Canning  and  Evaporation ; 
Preparation  of  Fruit-Butters,  Jellies,  Marmalades,  Catchups,  Pickles, 
Mustards,  etc.  '  Edited  from  various  sources.  By  WILLIAM  T. 
BRANNT.  Illustrated  by  79  Engravings.  479  pp.  8vo.  $5.00 

BRANNT.— The  Metal  Worker's    Handy-Book   of  Receipts 

and  Processes : 

Being  a  Collection  of  Cliemical  Formulas  and  Practical  Manipula- 
tions for  the  working  of  all  Metals;  including  the  Decoration  and 
Beautifying  of  Articles  Manufactured  therefrom,  as  well  as  their 
Preservation.  Edited  from  various  sources.  By  WILLIAM  T. 
BRANNT.  Illustrated.  I2mo.  $2.50 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.       3I 

DEITE. — A  Practical  Treatise  on  the  Manufacture  cf  Per* 

fumery : 

Comprising  directions  for  making  all  kinds  of  Perfumes,  Sachet 
Powders,  Fumigating  Materials,  Dentifrices,  Cosmetics,  etc.,  with  a 
full  account  of  the  Volatile  Oils,  Balsams,  Resins,  and  other  Natural 
and  Artificial  Perfume-substances,  including  the  Manufacture  of 
Fruit  Ethers,  and  tests  of  their  purity.  By  Dr.  C.  DEITE,  assisted 
by  L.  BORCHERT,  F.  EICHBAUM,  E.  KUGLER,  H.  TOEFFNER,  and 
other  experts.  From  the  German,  by  WM.  T.  BRANNT.  28  Engrav- 
ings. 358  pages.  8vo. 13-00 

EDWARDS. — American    Marine   Engineer,    Theoretical   and 

Practical : 

With  Examples  of  the  latest  and  most  approved  American  Practice. 
By  EMORY  EDWARDS.  85  illustrations.  I2mo.  .  .  $2.50 

EDWARDS. — 900    Examination   Questions  and   Answers: 

For  Engineers  and  Firemen  (Land  and  Marine)  who  desire  to  ob- 
tain a  United  States  Government  or  State  License.  Pocket-book 

form,  gilt  edge *         .         .         $1.5° 

POSSELT.— Technology  of  Textile  Design  : 

Being  a  Practical  Treatise  on  the  Construction  and  Application  of 
Weaves  for  all  Textile  Fabrics,  with  minute  reference  to  the  latest 
Inventions  for  Weaving.  Containing  also  an  Appendix,  showing 
the  Analysis  and  giving  the  Calculations  necessary  for  the  Manufac. 
tuie  of  the  various  Textile  Fabrics.  By  £.  A.  POSSELT,  Head 
Master  Textile  Department,  Pennsylvania  Museum  and  School  of 
Industrial  Art,  Philadelphia,  with  over  looo  illustrations.  292 
pages.  410 $5«oc 

POSSELT. — The  Jacquard  Machine  Analysed  and  Explained: 
With  an  Appendix  on  the  Preparation  of  Jacquard  Cards,  and 
Practical  Hints  to  Learners  of  Jacquard  Designing.  By  E.  A. 
POSSELT.  With  230  illustrations  and  numerous  diagrams.  127  pp. 
4to #3-00 

POSSELT. — The  Structure  of  Fibres,  Yarns  and  Fabrics: 
Being  a  Practical  Treatise  for  the  Use  of  all  Persons  Employed  in 
the  Manufacture  of  Textile  Fabrics,  containing  a  Description  of  the 
Growth  and  Manipulation  of  Cotton,  Wool,  Worsted,  Silk.  Flax, 
Jute,  Ramie,  China  Grass  and  Hemp,  and  Dealing  with  all  Manu- 
facturers' Calculations  for  Every  Class  of  Material,  also  Giving 
Minute  Details  for  the  Structure  of  all  kinds  of  Textile  Fabrics,  and 
an  Appendix  of  Arithmetic,  specially  adapted  for  Textile  Purposes. 
ByE.  A.  POSSELT.  Over  400  Illustrations,  quarto.  .  '$$.00 

RICH. — Artistic  Horse-Shoeing: 

A  Practical  and  Scientific  Treatise,  giving  Improved  Methods  of 
Shoeing,  with  Special  Directions  for  Shaping  Shoes  to  Cure  Different 
Diseases  of  the  Foot,  and  for  the  Correction  of  Faulty  Action  in 
Trotters.  By  GEORGE  E.  RICH.  62  Illustrations.  153  pages. 

.     I2mo 


32       HENRY  CAREY   BAIRD  &  CO.'S  CATALOGUE. 

RICH ARDSON.— Practical  Blacksmithing : 

A  Collection  of  Articles  Contributed  at  Different  Times  by  Skilled 
Workmen  to  the  columns  of  "  The  Blacksmith  and  Wheelwright," 
and  Covering  nearly  the  Whole  Range  of  Blacksmithing,  from  the 
Simplest  Job  of  Work  to  some  of  the  Most  Complex  Forging*. 
Compiled  and  Edited  by  M.  T.  RICHARDSON. 

Vol.1.  210  Illustrations.  224  pages.  I2mo.  .  .  $1.00 
Vol.  IT.  230  Illustrations.  262  pages.  I2mo.  .  .  $1.00 
Vol.  III.  390  Illustrations.  307  pages.  I2mo.  ,  .  $i .00 
Vol.  IV.  226  Illustrations.  276  pages.  lamo.  .  .  $1.00 

RICHARDSON.— The  Practical  Horseshoer: 

Being  a  Collection  of  Articles  on  Horseshoeing  in  all  its  Branchei 
which  have  appeared  from  time  to  time  in  the  columns  of  "  1  he 
Blacksmith  and  Wheelwright,"  etc.  Compiled  and  edited  by  M.  T. 
RICHARDSON.  174  illustrations. $1.00 

ROPER. — Instructions    and    Suggestions    for   Engineers   and 

Firemen : 
By  STEPHEN   ROPER,   Engineer.     i8mo.     Morocco         .         #2.00 

ROPER.— The  Steam  Boiler:  Its  Care  and  Management: 
By  STEPHEN  ROPER,  Engineer.     I2mo.,  tuck,  gilt  edges.         $2.00 

ROPER. — The  Young  Engineer's  Own  Book: 

Containing  an  Explanation  of  the  Principle  and  Theories  on  which 
the  Steam  Engine  as  a  Prime  Mover  is  Based.  By  STEPHEN  ROPER, 
Engineer.  160  illustrations,  363  pages.  i8mo.,  tuck  .  $3.00 

ROSE. — Modern  Steam -Engines: 

An  Elementary  Treatise  upon  the  Steam-Engine,  written  in  Plain 
language ;  for  Use  in  the  Workshop  as  well  as  in  the  Drawing  Office. 
Giving  Full  Explanations  of  the  Construction  of  Modern  Steanv 
Engines  :  Including  Diagrams  showing  their  Actual  operation.  To- 
gether with  Complete  but  Simple  Explanations  of  the  operations  of 
Various  Kinds  of  Valves,  Valve  Motions,  and  Link  Motions,  etc., 
thereby  Enabling  the  Ordinary  Engineer  to  clearly  Understand  the 
Principles  Involved  in  their  Construction  and  Use,  and  to  Plot  out 
their  Movements  upon  the  Drawing  Board.  By  JOSHUA  ROSE.  M.  E. 
Illustrated  by  422  engravings.  Revised.  358  pp.  .  .  #6.00 

ROSE. — Steam  Boilers: 

A  Practical  Treatise  on  Boiler  Construction  and  Examination,  for  the 
Use  of  Practical  Boiler  Makers,  Boiler  Users,  and  Inspectors;  and 
embracing  in  plain  figures  all  the  calculations  necessary  in  Designing 
or  Classifying  Steam  Boilers.  By  JOSHUA  ROSE,  M.  E.  Illustrated 
by  73  engravings.  250  pages.  8vo $2. 50 

6CHRIBER.— The  Complete  Carriage  and  Wagon  Painter: 
A  Concise  Compendium  of  the  Art  of  Painting  Carriages,  Wagons, 
and  Sleighs,  embracing  Full  Directions  in  all  the  Various  Branches, 
including  Lettering,  Scrolling,  Ornamenting,  Striping,  Varnishing, 
and  Coloring,  with  numerous  Recipes  for  Mixing  Colors.  73  Illus- 
trations. 177  pp.  I2mo £1.00 


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